UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act File Number: 811- 08012

Government Obligations Portfolio

(Exact Name of registrant as Specified in Charter)

The Eaton Vance Building, 255 State Street, Boston, Massachusetts 02109

(Address of Principal Executive Offices)

Alan R. Dynner

The Eaton Vance Building, 255 State Street, Boston, Massachusetts 02109

(Name and Address of Agent for Services)

(617) 482-8260

(registrant’s Telephone Number)

October 31

Date of Fiscal Year End

April 30, 2006

Date of Reporting Period

⁽³⁾Security (or a portion thereof) has been segregated to cover margin requirements on open financial futures contracts.

⁽²⁾ The Portfolio adopted the provisions of the revised AICPA Audit and Accounting Guide for Investment Companies and began amortizing market premium on fixed income securities. Additionally, the Portfolio reclassified net losses realized on prepayments received on mortgage-backed securities that were previously included in realized gains/losses to interest income. The effect of these changes for the year ended December 31, 2001 was a decrease in the ratio of net investment income to average net assest from 7.51% to 5.91%.

⁽⁵⁾ Total return is required to be disclosed for fiscal years beginning after December 15, 2000. Total return is not computed on an annualized basis.

Government Obligations Portfolio (the Portfolio) is registered under the Investment Company Act of 1940, as amended, as a diversified open-end management investment company. The Portfolio, which was organized as a trust under the laws of the State of New York in 1992, seeks to achieve a high current return by investing primarily in mortgage-backed securities (MBS) issued, backed or otherwise guaranteed by the U.S. government or its agencies or instrumentalities. The Declaration of Trust permits the Trustees to issue beneficial interests in the Portfolio. At April 30, 2006, the Eaton Vance Government Obligations Fund had a 85.7% interest in the Portfolio. The following is a summary of significant accounting policies of the Portfolio. The policies are in conformity with accounting principles generally accepted in the United States of America.

A Investment Valuation — Debt securities (including collateralized mortgage obligations and certain mortgage backed securities ("MBS")) normally are valued by independent pricing services. The pricing services consider various factors relating to bonds or loans and/or market transactions to determine market value. Most seasoned MBS are valued by the investment adviser's matrix pricing system. The matrix pricing system also considers various factors relating to bonds and market transactions to determine market value. Options are valued at last sale price on a U.S. exchange or board of trade or, in the absence of a sale, at the mean between the last bid and asked price. Financial futures contracts listed on commodity exchanges are valued at closing settlement prices. Securities for which there is no such quotation or valuation are valued at fair value using methods determined in good faith by or at the direction of the Trustees. Short-term obligations having remaining maturities of 60 days or less are valued at amortized cost, which approximates value. If short-term debt securities are acquired with a remaining maturity of more than 60 days, they will be valued by a pricing service.

B Income — Interest income is determined on the basis of interest accrued, adjusted for amortization of premium or accretion of discount.

C Federal Taxes — The Portfolio has elected to be treated as a partnership for federal tax purposes. No provision is made by the Portfolio for federal or state taxes on any taxable income of the Portfolio because each investor in the Portfolio is ultimately responsible for the payment of any taxes on its share of taxable income. Since at least one of the Portfolio's investors is a regulated investment company that invests all or substantially all of its assets in the Portfolio, the Portfolio normally must satisfy the applicable source of income and diversification requirements (under the Internal Revenue Code) in order for its investors to satisfy them. The Portfolio will allocate, at least annually among its investors, each investor's distributive share of the Portfolio's net investment income, net realized capital gains, and any other items of income, gain, loss, deduction or credit.

D Expense Reduction — Investors Bank & Trust Company (IBT) serves as custodian of the Portfolio. Pursuant to the custodian agreement, IBT receives a fee reduced by credits which are determined based on the average daily cash balance the Portfolio maintains with IBT. All credit balances used to reduce the Portfolio's custodian fees are reported as a reduction of expenses in the Statement of Operations. For the six months ended April 30, 2006, $328 in credit balances were used to reduce the Portfolio's custodian fee.

E Written Options — Upon the writing of a call or a put option, an amount equal to the premium received by the Portfolio is included in the Statement of Assets and Liabilities as a liability. The amount of the liability is subsequently marked-to-market to reflect the current value of the option written in accordance with the Portfolio's policies on investment valuations discussed above. Premiums received from writing options which expire are treated as realized gains. Premiums received from writing options which are exercised or are closed are added to or offset against the proceeds or amount paid on the transaction to determine the realized gain or loss. If a put option is exercised, the premium reduces the cost basis of the securities purchased by the Portfolio. The Portfolio, as writer of an option, may have no control over whether the underlying securities may be sold (call) or purchased (put) and, as a result, bears the market risk of an unfavorable change in the price of the securities underlying the written option.

F Purchased Options — Upon the purchase of a call or put option, the premium paid by the Portfolio is included in the Statement of Assets and Liabilities as an investment. The amount of the investment is subsequently marked-to-market to reflect the current market value of the option purchased, in accordance with the Portfolio's policies on investment valuations discussed above. If an option which the Portfolio has purchased expires on the stipulated expiration date, the Portfolio will realize a loss in the amount of the cost of the option. If the Portfolio enters into a closing sale transaction, the Portfolio will realize a

gain or loss, depending on whether the sales proceeds from the closing sale transaction are greater or less than the cost of the option. If a Portfolio exercises a put option, it will realize a gain or loss from the sale of the underlying security, and the proceeds from such sale will be decreased by the premium originally paid. If the Portfolio exercises a call option, the cost of the security which the Portfolio purchases upon exercise will be increased by the premium originally paid.

G Financial Futures Contracts — Upon entering into a financial futures contract, the Portfolio is required to deposit an amount (initial margin) either in cash or securities equal to a certain percentage of the purchase price indicated in the financial futures contract. Subsequent payments are made or received by the Portfolio (margin maintenance) each day, dependent on the daily fluctuations in the value of the underlying securities, and are recorded for book purposes as unrealized gains or losses by the Portfolio.

If the Portfolio enters into a closing transaction, the Portfolio will realize, for book purposes, a gain or loss equal to the difference between the value of the financial futures contract to sell and the financial futures contract to buy. The Portfolio's investment in financial futures contracts is designed only to hedge against anticipated future changes in interest rates. Should interest rates move unexpectedly, the Portfolio may not achieve the anticipated benefits of the financial futures contracts and may realize a loss.

H Other — Investment transactions are accounted for on the date the securities are purchased or sold. Realized gains and losses on securities sold are determined on the basis of identified cost.

I Use of Estimates — The preparation of the financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of income and expense during the reporting period. Actual results could differ from those estimates.

J Indemnifications — Under the Portfolio's organizational documents, its officers and Trustees may be indemnified against certain liabilities and expenses arising out of the performance of their duties to the Portfolio. Interestholders in the Portfolio are jointly and severally liable for the liabilities and obligations of the Portfolio in the event that the Portfolio fails to satisfy such liabilities and obligations; provided, however, that, to the extent assets are available in the Portfolio, the Portfolio may, under certain circumstances, indemnify interestholders from and against any claim or liability to which such holder may become subject by reason of being or having been an interestholder in the Portfolio. Additionally, in the normal course of business, the Portfolio enters into agreements with service providers that may contain indemnification clauses. The Portfolio's maximum exposure under these arrangements is unknown as this would involve future claims that may be made against the Portfolio that have not yet occurred.

K Statement of Cash Flows — The cash amount shown in the Statement of Cash Flows is the amount included in the Portfolio's Statement of Assets and Liabilities and represents cash on hand at its custodian and does not include any short-term investments at April 30, 2006.

L Interim Financial Statements — The interim financial statements relating to April 30, 2006 and for the six months then ended have not been audited by an independent registered public accounting firm, but in the opinion of the Portfolio's management reflect all adjustments, consisting only of normal recurring adjustments, necessary for the fair presentation of the financial statements.

Purchases and sales of investments, other than short-term obligations and including paydowns, aggregated $17,026,177 and $273,459,174, respectively.

The investment adviser fee is earned by Boston Management and Research (BMR), a wholly-owned subsidiary of Eaton Vance Management (EVM), as compensation for management and investment advisory services rendered to the Portfolio. Under its investment advisory agreement with the Portfolio, BMR receives a fee computed at the monthly rate of 0.0625% (0.75% per annum) of the Portfolio's average daily net assets up to $500 million. On net assets of $500 million or more, BMR has contractually agreed to reduce its advisory fee as follows: 0.6875% annually on average daily net assets of $500 million but less than $1 billion; 0.6250% of average daily net assets of $1 billion but less than $1.5 billion; 0.5625% of average daily net assets of $1.5 billion but less than $2 billion; 0.5000% of average daily net assets of $2 billion but less than $2.5 billion; and

0.4375% of average daily net assets of $2.5 billion and over. These contractual fee reductions cannot be terminated or decreased without the express consent of the Portfolio's Board of Trustees and its shareholders and are intended to continue indefinitely. For the six months ended April 30, 2006, the fee was equivalent to 0.73% (annualized) of the Portfolio's average net assets for such period and amounted to $2,976,126. Except as to Trustees of the Portfolio who are not members of EVM's or BMR's organization, officers and Trustees receive remuneration for their services to the Portfolio out of such investment adviser fee. Trustees of the Portfolio that are not affiliated with the Investment Adviser may elect to defer receipt of all or a percentage of their annual fees in accordance with the terms of the Trustees Deferred Compensation Plan. For the six months ended April 30, 2006, no significant amounts have been deferred.

Certain officers and Trustees of the Portfolio are officers of the above organizations.

The Portfolio participates with other portfolios and funds managed by BMR and EVM and its affiliates in a $150 million unsecured line of credit agreement with a group of banks. Borrowings will be made by the Portfolio solely to facilitate the handling of unusual and/or unanticipated short term cash requirements. Interest is charged to each participating portfolio or fund based on its borrowings at an amount above either the Eurodollar rate or federal funds rate. In addition, a fee computed at an annual rate of 0.10% on the daily unused portion of the line of credit is allocated among the participating portfolios and funds at the end of each quarter. The average daily loan balance for the six months ended April 30, 2006 was $249,724 and the average interest rate was 4.36%.

The Portfolio has established a securities lending agreement with brokers in which the Portfolio lends portfolio securities to a broker in exchange for collateral consisting of either cash or U.S. government securities in an amount at least equal to the market value of the securities on loan. Under the agreement, the Portfolio continues to earn interest on the securities loaned. Collateral received is generally cash, and the Portfolio invests the cash in accordance with the Portfolio's investment objective and policies and receives any interest on the amount invested but it must also pay the broker a loan rebate fee computed as a varying percentage of the collateral received. The loan rebate fee paid by the Portfolio offsets a portion of the interest income received and amounted to $5,662,370 for the six months ended April 30, 2006. At April 30, 2006, the value of the securities loaned and the value of the collateral amounted to $187,033,342 and $191,486,676, respectively. In the event of counterparty default, the Portfolio is subject to potential loss if it is delayed or prevented from exercising its right to dispose of the collateral. The Portfolio bears risk in the event that invested collateral is not sufficient to meet obligations due on the loans.

The cost and unrealized appreciation (depreciation) in value of the investments owned at April 30, 2006, as determined on a federal income tax basis, were as follows:

The Portfolio regularly trades in financial instruments with off-balance sheet risk in the normal course of its investing activities to assist in managing exposure to various market risks. These financial instruments include written options and financial futures contracts, and may involve, to a varying degree, elements of risk in excess of the amounts recognized for financial statement purposes. The notional or contractual amounts of these instruments represent the investment the Portfolio has in particular classes of financial instruments and does not necessarily represent the amounts potentially subject to risk. The measurement of the risks associated with these instruments is meaningful only when all related and offsetting transactions are considered. A summary of obligations under these financial instruments at April 30, 2006 is as follows:

At April 30, 2006, the Portfolio had sufficient cash and/or securities to cover margin requirements on any open futures contracts.

The Investment Company Act of 1940, as amended (the "1940 Act"), provides, in substance, that each investment advisory agreement between a fund and its investment adviser will continue in effect from year to year only if its continuance is approved at least annually by the fund's board of trustees, including by a vote of a majority of the trustees who are not "interested persons" of the fund ("Independent Trustees") cast in person at a meeting called for the purpose of considering such approval.

At a meeting of the Boards of Trustees (each a "Board") of the Eaton Vance group of mutual funds (the "Eaton Vance Funds") held on March 27, 2006, the Board, including a majority of the Independent Trustees, voted to approve continuation of existing advisory and sub-advisory agreements for the Eaton Vance Funds for an additional one-year period. In voting its approval, the Board relied upon the affirmative recommendation of the Special Committee of the Board, which is a committee comprised exclusively of Independent Trustees. Prior to making its recommendation, the Special Committee reviewed information furnished for a series of meetings of the Special Committee held in February and March 2006. Such information included, among other things, the following:

• An independent report comparing the advisory and related fees paid by each fund with fees paid by comparable funds;

• An independent report comparing each fund's total expense ratio and its components to comparable funds;

• An independent report comparing the investment performance of each fund to the investment performance of comparable funds over various time periods;

• Data regarding investment performance in comparison to relevant peer groups of funds and appropriate indices;

• Comparative information concerning fees charged by each adviser for managing other mutual funds and institutional accounts using investment strategies and techniques similar to those used in managing the fund;

• Profitability analyses for each adviser with respect to each fund managed by it;

• Descriptions of the investment management services provided to each fund, including the investment strategies and processes employed;

• Information concerning the allocation of brokerage and the benefits received by each adviser as a result of brokerage allocation, including information concerning the acquisition of research through "soft dollar" benefits received in connection with the funds' brokerage, and the implementation of a soft dollar reimbursement program established with respect to the funds;

• The procedures and processes used to determine the fair value of fund assets and actions taken to monitor and test the effectiveness of such procedures and processes;

• Descriptions of the qualifications, education and experience of the individual investment professionals whose responsibilities include portfolio management and investment research for the funds, and information relating to their compensation and responsibilities with respect to managing other mutual funds and investment accounts;

• Copies of the Codes of Ethics of each adviser and its affiliates, together with information relating to compliance with and the administration of such codes;

• Information concerning the resources devoted to compliance efforts undertaken by each adviser and its affiliates on behalf of the funds (including descriptions of various compliance programs) and their record of compliance with investment policies and restrictions, including policies with respect to market-timing, late trading and selective portfolio disclosure, and with policies on personal securities transactions;

• Descriptions of the business continuity and disaster recovery plans of each adviser and its affiliates;

• Information concerning the nature, cost and character of the administrative and other non-investment management services provided by Eaton Vance Management and its affiliates;

• Information concerning management of the relationship with the custodian, subcustodians and fund accountants by each adviser or the funds' administrator; and

2006, the Board met nine times and the Special Committee, the Audit Committee and the Governance Committee, each of which is a Committee comprised solely of Independent Trustees, met eight, twelve and five times, respectively. At such meetings, the Trustees received, among other things, presentations by the portfolio managers and other investment professionals of each adviser relating to the investment performance of each fund and the investment strategies used in pursuing the fund's investment objective.

For funds that invest through one or more underlying portfolios, the Board considered similar information about the portfolio(s) when considering the approval of advisory agreements. In addition, in cases where the fund's investment adviser has engaged a sub-adviser, the Board considered similar information about the sub-adviser when considering the approval of any sub-advisory agreement.

The Special Committee was assisted throughout the contract review process by Goodwin Procter LLP, legal counsel for the Independent Trustees. The members of the Special Committee relied upon the advice of such counsel and their own business judgment in determining the material factors to be considered in evaluating each advisory and sub-advisory agreement and the weight to be given to each such factor. The conclusions reached with respect to each advisory and sub-advisory agreement were based on a comprehensive evaluation of all the information provided and not any single factor. Moreover, each member of the Special Committee may have placed varying emphasis on particular factors in reaching conclusions with respect to each advisory and sub-advisory agreement.