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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

For the Quarterly Period Ended March 31, 2013

Commission File No. 0-21886

BARRETT BUSINESS SERVICES, INC.

(Exact name of registrant as specified in its charter)

(360) 828-0700

(Registrant’s telephone number, including area code)

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  x    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Website, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or such shorter period that the registrant was required to submit and post such files).    Yes  x    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company (as defined in Rule 12b-2 of the Exchange Act).

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  x

Number of shares of common stock, $.01 par value, outstanding at April 30, 2013 was 7,044,131 shares.

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BARRETT BUSINESS SERVICES, INC.

INDEX

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Part I - Financial Information

BARRETT BUSINESS SERVICES, INC.

Consolidated Balance Sheets

(Unaudited)

(In thousands, except per share amounts)

The accompanying notes are an integral part of these financial statements

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BARRETT BUSINESS SERVICES, INC.

Consolidated Statements of Operations

(Unaudited)

(In thousands, except per share amounts)

The accompanying notes are an integral part of these financial statements

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BARRETT BUSINESS SERVICES, INC.

Consolidated Statements of Comprehensive Loss

(Unaudited)

(In thousands)

The accompanying notes are an integral part of these financial statements

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BARRETT BUSINESS SERVICES, INC.

Consolidated Statements of Stockholders’ Equity

Three Months Ended March 31, 2013 and 2012

(Unaudited)

(In thousands)

The accompanying notes are an integral part of these financial statements

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BARRETT BUSINESS SERVICES, INC.

Consolidated Statements of Cash Flows

(Unaudited)

(In thousands)

The accompanying notes are an integral part of these financial statements

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BARRETT BUSINESS SERVICES, INC.

Notes to Consolidated Financial Statements (Unaudited)

Note 1 - Basis of Presentation of Interim Period Statements

The accompanying consolidated financial statements are unaudited and have been prepared by Barrett Business Services, Inc. (“Barrett”, “BBSI”, the “Company”, “our” or “we”), pursuant to the rules and regulations of the Securities and Exchange Commission. Certain information and note disclosures typically included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, the consolidated financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the results for the interim periods presented. The preparation of financial statements in conformity with generally accepted accounting principles (“GAAP”) requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results may differ from such estimates and assumptions. The consolidated financial statements should be read in conjunction with the audited financial statements and notes thereto included in the Company’s 2012 Annual Report on Form 10-K at pages F1 – F29. The results of operations for an interim period are not necessarily indicative of the results of operations for a full year.

Revenue recognition

We recognize revenue as services are rendered by our workforce. Professional employer services are normally used by organizations to satisfy ongoing human resource management needs and typically involve contracts with a minimum term of one year, which cover all employees at a particular work site. Our client services agreements are renewable on an annual basis and typically require 30 days’ written notice to cancel or terminate the contract by either party. Our client services agreements provide for immediate termination upon any default of the client regardless of when notice is given. We report professional employer services revenues on a net basis because we are not the primary obligor for the services provided by our co-employed clients to their customers pursuant to our client services agreements. Consequently, our professional employer service revenues represent the gross margin generated from our professional employer services after deducting the amounts invoiced to clients for direct payroll expenses such as salaries and wages and safety incentives. These amounts are also excluded from cost of revenues. Professional employer service revenues also include amounts invoiced to our clients for employer payroll-related taxes and workers’ compensation coverage. Staffing services are engaged by customers to meet short-term and long-term personnel needs.

Marketable securities

As of March 31, 2013, the Company’s marketable securities consisted of tax-exempt municipal securities, U.S. treasuries and corporate bonds. The Company classifies municipal securities, U.S. treasuries, and certain of its corporate bonds as available for sale; they are reported at fair value with unrealized gains and losses, net of taxes, shown as a component of accumulated other comprehensive income (loss) in stockholders’ equity. In the event a loss is determined to be other-than-temporary, the loss will be recognized in the statement of operations. Certain of the Company’s corporate bonds are classified as held-to-maturity and are reported at amortized cost.

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BARRETT BUSINESS SERVICES, INC.

Notes to Consolidated Financial Statements (Unaudited) (Continued)

Note 1 - Basis of Presentation of Interim Period Statements (Continued)

Allowance for doubtful accounts

The Company had an allowance for doubtful accounts of $383,000 and $381,000 at March 31, 2013 and December 31, 2012, respectively. The Company must make estimates of the collectibility of accounts receivable. Management analyzes historical bad debts, customer concentrations, customer creditworthiness, current economic conditions and changes in customers’ payment trends when evaluating the adequacy of the allowance for doubtful accounts. The Company deems an account balance uncollectible only after it has pursued all available assets of the customer and, where applicable, the assets of the personal guarantor.

Workers’ compensation claims

The Company is a self-insured employer with respect to workers’ compensation coverage for all of its employees (including employees co-employed through our client service agreements) working in California, Oregon, Maryland, Delaware and Colorado. In the state of Washington, state law allows only the Company’s staffing services and internal management employees to be covered under the Company’s self-insured workers’ compensation program. Additionally, the Company operates a wholly-owned fully licensed insurance company, Ecole Insurance Company (“Ecole”), in Arizona to provide workers’ compensation coverage to our employees in Arizona.

To manage our financial exposure, in the event of catastrophic injuries or fatalities, the Company maintains excess workers’ compensation insurance through our wholly owned captive insurance company, Associated Insurance Company for Excess (“AICE”), with a per occurrence retention of $5.0 million, except in Maryland and Colorado, where our per occurrence retention is $1.0 million and $500,000, respectively. AICE maintains excess workers’ compensation insurance coverage with ACE American Insurance Company (“ACE”), between $5.0 million and $15.0 million per occurrence, except in Maryland, where coverage with ACE is between $1.0 million and $25.0 million per occurrence, and in Colorado, where the coverage with ACE is between $500,000 and statutory limits per occurrence. The Company continues to evaluate the financial capacity of its insurers to assess the recoverability of the related insurer receivables.

The Company has provided a total of $77.2 million and $70.6 million at March 31, 2013 and December 31, 2012, respectively, as an estimated future liability for unsettled workers’ compensation claims liabilities. The estimated liability for unsettled workers’ compensation claims represents management’s best estimate based upon an actuarial valuation provided by a third party actuary. Included in the claims liabilities are case reserve estimates for reported losses, plus additional amounts based on projections for incurred but not reported claims and anticipated increases in case reserve estimates. Also included in these estimates are amounts for unallocated loss adjustment expenses, including legal costs. These estimates are continually reviewed and adjustments to liabilities are reflected in current operating results as they become known.

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BARRETT BUSINESS SERVICES, INC.

Notes to Consolidated Financial Statements (Unaudited) (Continued)

Note 1 - Basis of Presentation of Interim Period Statements (Continued)

Safety incentives liability

Safety incentives represent cash incentives paid to certain client companies under client service agreements for maintaining safe-work practices in order to minimize workplace injuries, thereby meeting agreed-upon loss objectives. The Company has provided $10.3 million at March 31, 2013 and $9.8 million at December 31, 2012 as an estimate of the liability for unpaid safety incentives. The incentive is based on a percentage of annual payroll and is paid annually to customers who meet predetermined workers’ compensation claims cost objectives. Safety incentive payments are made only after closure of all workers’ compensation claims incurred during the customer’s contract period. The liability is estimated and accrued each month based upon the incentive earned less the then-current amount of the customer’s estimated workers’ compensation claims reserves as established by the Company’s internal and third-party claims administrators, and the expected payout as determined by historical incentive payment trends. Safety incentive expense is netted against professional employer services revenue in our consolidated statements of operations.

Reclassifications

Certain prior year amounts have been reclassified to conform with the 2013 presentation. Such reclassifications had no impact on the Company’s financial condition, operating results, cash flows, working capital or stockholders’ equity.

Note 2 – Stock Repurchase

Effective March 28, 2012, the Company repurchased 2,485,929 shares of the Company’s common stock held by the Estate of William W. Sherertz and 500,000 common shares held by Nancy Sherertz. Mr. Sherertz, a founder and former president and CEO of the Company, died January 20, 2011. Nancy Sherertz is also a founder of the Company. The common shares were repurchased at a price of $20 per share, representing total consideration of $59.7 million. The Company used a combination of $24.9 million in cash and issued 34,800 shares of Series A Nonconvertible, Non-Voting Redeemable Preferred Stock with a liquidation preference of $1,000 per share. Additionally, the Company incurred professional and legal fees totaling $514,000 related to the transaction.

Effective September 21, 2012, the Company redeemed all of the outstanding shares of its Series A Nonconvertible, Non-Voting Redeemable Preferred Stock for $34.8 million using a combination of cash on hand and availability under a new revolving credit facility provided by its principal bank. By redeeming the preferred stock within six months of issuance, the Company was not required to pay a semi-annual dividend of approximately $870,000 due September 28, 2012.

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BARRETT BUSINESS SERVICES, INC.

Notes to Consolidated Financial Statements (Unaudited) (Continued)

Note 3 – Revolving Credit Facility

The Company maintains a credit agreement (the “Agreement”) with its principal bank, Wells Fargo Bank, National Association (the “Bank”). The Agreement, which expires October 1, 2017, provides for a revolving credit facility with initial borrowing capacity of up to $24.0 million. The Company had no outstanding borrowings on the revolving credit facility at March 31, 2013. The Agreement also provides for the continuance of existing standby letters of credit in connection with various surety deposit requirements for workers’ compensation purposes, as to which the amount outstanding totaled approximately $23.8 million at March 31, 2013.

Advances under the revolving credit facility bear interest, at the Company’s option, at either (a) a fixed rate for a term selected by the Company from time-to-time or (b) a fluctuating rate. In each case, the rate is calculated based on LIBOR plus 1.75%. The Agreement also provides for an unused commitment fee of 0.25% per annum on the average daily unused amount of the revolving credit facility.

The credit facility is collateralized by the Company’s accounts receivable and other rights to receive payment, general intangibles, inventory and equipment. Under the Agreement, the maximum principal amount available will be reduced by $2.5 million every six months commencing April 1, 2013.

The Agreement, as amended, requires the satisfaction of certain financial covenants as follows:

The Agreement also contains customary events of default. If an event of default under the Agreement occurs and is continuing, the Bank may declare any outstanding obligations under the Agreement to be immediately due and payable. The Company was in compliance with all applicable financial covenants at March 31, 2013.

Note 4 - Basic and Diluted Earnings Per Share

Basic earnings per share are computed based on the weighted average number of common shares outstanding during the period. Diluted earnings per common share reflect the potential effects of the exercise of outstanding stock options and vesting of restricted stock units. Basic and diluted common shares outstanding are summarized as follows:

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BARRETT BUSINESS SERVICES, INC.

Notes to Consolidated Financial Statements (Unaudited) (Continued)

Note 4 - Basic and Diluted Earnings Per Share (Continued)

As a result of the net loss reported for the three months ended March 31, 2013 and 2012, 291,056 and 112,894 potential common shares, respectively, have been excluded from the calculation of diluted loss per common share because their effect would be anti-dilutive.

Note 5- Workers’ Compensation

The following table summarizes the aggregate workers’ compensation reserve activity (in thousands):

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BARRETT BUSINESS SERVICES, INC.

Notes to Consolidated Financial Statements (Unaudited) (Continued)

Note 6 - Fair Value Measurement

Marketable securities consist of the following investments (in thousands):

The Company’s restricted marketable securities component of restricted marketable securities and workers’ compensation deposits consists of the following (in thousands):

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Overview

Barrett Business Services, Inc. (“BBSI,” the “Company,” “our” or “we”), was incorporated in the state of Maryland in 1965. We are a leading provider of business management solutions, combining human resource outsourcing and professional management consulting to create an operational platform that differentiates us from our competitors. Our integrated platform is grounded in expertise in payroll processing, employee benefits, workers’ compensation coverage, risk management and workplace safety programs, human resource administration, recruiting and permanent placement. BBSI helps small-to medium-sized businesses improve the efficiency of their operations. Our principal services assist our clients in leveraging their investment in human capital. We believe that our combination of business management solutions and expertise in human capital management enables us to provide our clients with a unique blend of services not offered by our competitors.

Our Services

Our passage from an entrepreneurially run company to a professionally managed organization has helped to form our view that all businesses experience the same success factors in their growth, as well as the same potential pitfalls. The insights gained through our own growth, along with the trends we see in working with more than 3,000 companies each day, define our approach to guiding business owners through the challenges associated with being an employer.

Through our client services agreement, the Company enters into a contract to become a co-employer of the client’s existing workforce assuming responsibility for payroll, payroll taxes, workers’ compensation coverage and certain other administrative functions, while the business owner client maintains physical care, custody and control of their workforce, including the authority to hire and terminate employees. Staffing services include on-demand or short-term staffing assignments, and long or indefinite-term contract staffing. The Company’s staffing services also include recruiting, which involves fee-based search efforts for specific employee candidates at the request of co-employed clients, staffing customers or other businesses.

We believe the expert knowledge of our teams combined with tools from the HR outsourcing industry helps our clients more effectively leverage their internal resources. We assist our clients by:

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Our Services (Continued)

Prior to entering into a client services agreement, we perform an in-depth analysis of the potential client’s operations, including evaluation of needs and objectives, risk assessment and financial review. Once the client service agreement has been signed, we pair each of our clients with a dedicated, local branch-based business unit comprised of management professionals with expertise in Human Resource Consulting, Risk Consulting, Payroll, Benefits Administration and Recruiting. We believe our hands-on model allows our clients to more quickly adopt processes to develop a more productive workforce, mitigate workplace injury and risk and encourage workplace compliance with a broad range of employment and safety regulations.

The Company serves a growing and diverse client base of small and medium-sized businesses in a wide variety of industries through a network of branch offices in California, Oregon, Washington, Idaho, Arizona, Utah, Colorado, Maryland, Delaware and North Carolina. Barrett also has several smaller recruiting offices in its general market areas, which are under the direction of a branch office.

Results of Operations

The following table sets forth percentages of total revenues represented by selected items in the Company’s Consolidated Statements of Operations for the three months ended March 31, 2013 and 2012.

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Results of Operations (Continued)

We report professional employer services revenues on a net basis because we are not the primary obligor for the services provided by our co-employed clients to their customers pursuant to our client service agreements. The presentation of revenues on a net basis and the relative contributions of staffing and professional employer services revenues can create volatility in our gross margin percentage. The general impact of fluctuations in our revenue mix is described below.

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Results of Operations (Continued)

We present for comparison purposes the gross revenues and cost of revenues information set forth in the table below. Although not in accordance with GAAP, management believes this information is more informative as to the level of our business activity and more illustrative of how we manage our operations, including the preparation of our internal operating forecasts, because it presents our professional employer services on a basis comparable to our staffing services.

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Results of Operations (Continued)

A reconciliation of non-GAAP gross professional employer services revenues to net professional employer services revenues is as follows: