<PAGE>

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                    FORM 10-Q

           [X] QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

                  For the Quarterly Period Ended March 31, 2004

                                       OR

          [ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

   For the Transition Period from                     to
                                  -------------------    ---------------------

                         Commission File Number 0-13546

                               ------------------

                     APACHE OFFSHORE INVESTMENT PARTNERSHIP
                     --------------------------------------
             (Exact Name of Registrant as Specified in Its Charter)

                 Delaware                                       41-1464066
     -------------------------------                      ----------------------
     (State or Other Jurisdiction of                         (I.R.S. Employer
     Incorporation or Organization)                       Identification Number)

                                                                77056-4400
    Suite 100, One Post Oak Central                             ----------
 2000 Post Oak Boulevard, Houston, TX                            (Zip Code)
---------------------------------------
(Address of Principal Executive Offices)

       Registrant's Telephone Number, Including Area Code: (713) 296-6000

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 [ ]

<PAGE>

                         PART I - FINANCIAL INFORMATION

ITEM 1 - FINANCIAL STATEMENTS

                     APACHE OFFSHORE INVESTMENT PARTNERSHIP
                        STATEMENT OF CONSOLIDATED INCOME
                                   (UNAUDITED)

<TABLE>
<CAPTION>
                                                             FOR THE THREE MONTHS
                                                                ENDED MARCH 31,
                                                           ------------------------
                                                              2004          2003
                                                           ----------    ----------
<S>                                                        <C>           <C>
REVENUES:
    Oil and gas sales                                      $3,250,730    $3,191,408
    Interest income                                             6,084         3,438
                                                           ----------    ----------

                                                            3,256,814     3,194,846
                                                           ----------    ----------

EXPENSES:
    Depreciation, depletion and amortization                  689,206       741,464
    Asset retirement obligation accretion                      11,922         9,197
    Lease operating costs                                     198,610       257,611
    Gathering and transportation expense                       34,992        38,099
    Administrative                                            102,000       105,000
                                                           ----------    ----------

                                                            1,036,730     1,151,371
                                                           ----------    ----------

OPERATING INCOME BEFORE CUMULATIVE EFFECT
  OF CHANGE IN ACCOUNTING PRINCIPLE                         2,220,084     2,043,475
                                                           ----------    ----------

    Cumulative effect of change in accounting principle             -       302,407
                                                           ----------    ----------

NET INCOME                                                 $2,220,084    $2,345,882
                                                           ==========    ==========

NET INCOME ALLOCATED TO:
    Managing Partner                                       $  564,279    $  536,308
    Investing Partners                                      1,655,805     1,809,574
                                                           ----------    ----------

                                                           $2,220,084    $2,345,882
                                                           ==========    ==========

NET INCOME PER INVESTING PARTNER UNIT                      $    1,561    $    1,668
                                                           ==========    ==========

WEIGHTED AVERAGE INVESTING PARTNER
  UNITS OUTSTANDING                                           1,060.7       1,084.9
                                                           ==========    ==========
</TABLE>

                 The accompanying notes to financial statements
                     are an integral part of this statement.

                                       1

<PAGE>

                     APACHE OFFSHORE INVESTMENT PARTNERSHIP
                      STATEMENT OF CONSOLIDATED CASH FLOWS
                                   (UNAUDITED)

<TABLE>
<CAPTION>
                                                                               FOR THE THREE MONTHS
                                                                                  ENDED MARCH 31,
                                                                           ----------------------------
                                                                               2004            2003
                                                                           ------------    ------------
<S>                                                                        <C>             <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
    Net income                                                             $  2,220,084    $  2,345,882
    Adjustments to reconcile net income to net cash
       provided by operating activities:
          Depreciation, depletion and amortization                              689,206         741,464
          Asset retirement obligation accretion                                  11,922           9,197
          Cumulative effect of change in accounting principle                         -        (302,407)
          Dismantlement and abandonment cost                                   (146,222)              -
          Changes in operating assets and liabilities:
              (Increase) decrease in accrued revenues receivable                 18,345        (519,078)
              (Increase) decrease in receivable from/payable to
                Apache Corporation                                              (97,855)       (418,814)
              Increase (decrease) in accrued operating expenses payable           6,049          57,768
                                                                           ------------    ------------

          Net cash provided by operating activities                           2,701,529       1,914,012
                                                                           ------------    ------------

CASH FLOWS FROM INVESTING ACTIVITIES:
    Additions to oil and gas properties                                        (198,621)        (82,532)
                                                                           ------------    ------------

          Net cash used in investing activities                                (198,621)        (82,532)
                                                                           ------------    ------------

CASH FLOWS FROM FINANCING ACTIVITIES:
    Distributions to Investing Partners                                      (2,121,466)       (542,445)
    Distributions to Managing Partner                                          (581,420)       (463,526)
                                                                           ------------    ------------

          Net cash used in financing activities                              (2,702,886)     (1,005,971)
                                                                           ------------    ------------

NET INCREASE (DECREASE) IN CASH AND
  CASH EQUIVALENTS                                                             (199,978)        825,509

CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR                                  2,271,495         915,891
                                                                           ------------    ------------

CASH AND CASH EQUIVALENTS, END OF PERIOD                                   $  2,071,517    $  1,741,400
                                                                           ============    ============
</TABLE>

                 The accompanying notes to financial statements
                     are an integral part of this statement.

                                       2

<PAGE>

                     APACHE OFFSHORE INVESTMENT PARTNERSHIP
                           CONSOLIDATED BALANCE SHEET
                                   (UNAUDITED)

<TABLE>
<CAPTION>
                                                                    MARCH 31,     DECEMBER 31,
                                                                      2004           2003
                                                                  ------------    ------------
<S>                                                               <C>             <C>
                                  ASSETS
CURRENT ASSETS:
   Cash and cash equivalents                                      $  2,071,517    $  2,271,495
   Accrued revenues receivable                                         622,865         641,210
   Receivable from Apache Corporation                                  184,072          86,217
                                                                  ------------    ------------

                                                                     2,878,454       2,998,922
                                                                  ------------    ------------

OIL AND GAS PROPERTIES, on the basis of full cost accounting:
   Proved properties                                               182,537,535     182,173,899
   Less - Accumulated depreciation, depletion and amortization    (174,187,895)   (173,498,689)
                                                                  ------------    ------------

                                                                     8,349,640       8,675,210
                                                                  ------------    ------------

                                                                  $ 11,228,094    $ 11,674,132
                                                                  ============    ============

                    LIABILITIES AND PARTNERS' CAPITAL

CURRENT LIABILITIES:
   Accrued development costs                                      $    353,533    $    334,740
   Accrued operating expenses                                           58,125          52,076
                                                                  ------------    ------------

                                                                       411,658         386,816
                                                                  ------------    ------------

ASSET RETIREMENT OBLIGATION                                            824,442         812,520
                                                                  ------------    ------------

PARTNERS' CAPITAL:
   Managing Partner                                                    150,069         167,210
   Investing Partners (1,060.7 units outstanding)                    9,841,925      10,307,586
                                                                  ------------    ------------

                                                                     9,991,994      10,474,796
                                                                  ------------    ------------

                                                                  $ 11,228,094    $ 11,674,132
                                                                  ============    ============
</TABLE>

                 The accompanying notes to financial statements
                     are an integral part of this statement.

                                       3

<PAGE>

                     APACHE OFFSHORE INVESTMENT PARTNERSHIP
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                   (UNAUDITED)

      The financial statements included herein have been prepared by the Apache
Offshore Investment Partnership (the Partnership), without audit, pursuant to
the rules and regulations of the Securities and Exchange Commission, and reflect
all adjustments which are, in the opinion of management, necessary for a fair
statement of the results for the interim periods, on a basis consistent with the
annual audited financial statements. All such adjustments are of a normal,
recurring nature. Certain information, accounting policies, and footnote
disclosures normally included in financial statements prepared in accordance
with generally accepted accounting principles have been omitted pursuant to such
rules and regulations, although the Partnership believes that the disclosures
are adequate to make the information presented not misleading. These financial
statements should be read in conjunction with the financial statements and the
summary of significant accounting policies and notes thereto included in the
Partnership's latest annual report on Form 10-K.

1.    RECEIVABLE FROM APACHE CORPORATION

      The receivable from Apache Corporation, the Partnership's managing partner
(Apache or the Managing Partner), represents the net result of the Investing
Partners' revenue and expenditure transactions in the current month. Generally,
cash in this amount will be transferred to Apache in the month after the
Partnership's transactions are processed and the net results of operations are
determined.

2.    RIGHT OF PRESENTMENT

      As provided in the Partnership Agreement, as amended (the Amended
Partnership Agreement), a first right of presentment offer for 2004 of $11,518
per Unit, plus interest to the date of payment, was made to Investing Partners
in April 2004, based on a valuation date of December 31, 2003. The Partnership
is not in a position to predict how many Units will be presented for repurchase
under the April 2004 offer and cannot, at this time, determine if the
Partnership will have sufficient funds available to repurchase all Units
presented. The Investing Partners have until May 21, 2004 to offer their Units
under the current right of presentment. The Partnership has no obligation to
purchase any Units presented to the extent it determines that it has
insufficient funds for such purchases. The Amended Partnership Agreement
contains limitations on the number of Units that the Partnership can repurchase,
including a limit of 10 percent of the outstanding Units on an annual basis.

3.    ASSET RETIREMENT OBLIGATIONS

      Effective January 1, 2003, the Partnership adopted Statement of Financial
Accounting Standards (SFAS) No. 143, "Accounting for Asset Retirement
Obligations," which requires that an asset retirement obligation (ARO)
associated with the retirement of a tangible long-lived asset be recognized as a
liability in the period in which it is incurred and becomes determinable, with
an offsetting increase in the carrying amount of the associated asset. The cost
of the tangible asset, including the initially recognized ARO, is depleted such
that the cost of the ARO is recognized over the useful life of the asset. The
ARO is recorded at fair value, and accretion expense will be recognized over
time as the discounted liability is accreted to its expected settlement value.
The fair value of the ARO is measured using expected future cash outflows
discounted at the company's credit-adjusted risk-free interest rate. The
Partnership's asset retirement obligations primarily relate to the plugging and
abandonment of oil and gas properties.

      Upon adoption, the Partnership recorded an increase to net oil and gas
properties of $1.1 million and additional liabilities related to asset
retirement obligations of $.8 million. These amounts reflect the ARO of the
Partnership had the provisions of SFAS No. 143 been applied since inception and
resulted in a non-cash cumulative effect increase to 2003 earnings of $.3
million.

      The Partnership's increase in ARO liability from December 31, 2003 was
attributable to accretion expense of $11,922.

                                       4

<PAGE>

ITEM 2 - MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
         OF OPERATIONS

RESULTS OF OPERATIONS

NET INCOME AND REVENUE

      The Partnership reported net income for the first quarter of 2004 of $2.2
million, or $1,561 per Investing Partner Unit. A year ago, the Partnership
reported earnings of $2.3 million for the first quarter of 2003 which included
$.3 million of income from the cumulative effect of change in accounting
principle from the adoption of SFAS No. 143. Driven by higher oil prices,
increased production and lower expenses in 2004, net income in the current
quarter was nine percent higher than the first quarter of 2003 operating income
before the cumulative effect of change in accounting principle. Total revenue
increased two percent, rising from $3.2 million in the first quarter of 2003 to
$3.3 million in the first quarter of 2004.

      The Partnership's oil and gas production volume and price information is
summarized in the following table (gas volumes presented in thousand cubic feet
(Mcf) per day):

<TABLE>
<CAPTION>
                                                         FOR THE THREE MONTHS
                                                             ENDED MARCH 31,
                                                      ----------------------------     INCREASE
                                                          2004            2003        (DECREASE)
                                                      ------------    ------------    ----------
<S>                                                   <C>             <C>             <C>
Gas volume - Mcf per day                                     3,750           3,647             3%
Average gas price - per Mcf                           $       5.99    $       6.91           (13%)
Oil volume - barrels per day                                   338             309             9%
Average oil price - per barrel                        $      35.24    $      33.22             6%
Natural gas liquids (NGL) volume - barrels per day              48               -             -
Average NGL price - per barrel                        $      27.54               -             -
</TABLE>

OIL AND GAS SALES

      Natural gas sales for the first quarter of 2004 totaled $2.0 million, down
10 percent from the first quarter of 2003. The Partnership's average realized
natural gas price for the first quarter of 2004 decreased $.92 per Mcf from the
year-earlier period, reducing current sales by approximately $.3 million.
Natural gas volumes on a daily basis increased three percent from a year ago as
a result of recompletion operations in 2004 and 2003. The Partnership
recompleted the South Timbalier 295 A-13 ST1 and Ship Shoal 258 JB #5 wells in
February 2004.

      The Partnership's crude oil sales for the first quarter of 2004 totaled
$1.1 million, a 17 percent increase from the first quarter of 2003. A $2.02 per
barrel, or six percent, increase in the Partnership's average realized oil price
contributed to the increase in oil revenues. Oil production was nine percent
higher than a year ago as recompletions at South Timbalier 295 during the second
half of 2003 more than offset natural depletion.

      During the fourth quarter of 2003, the Partnership began processing a
portion of its natural gas production through on-shore plants operated by third
parties. The Partnership sold an average of 48 barrels per day of natural gas
liquids from processing gas during the first quarter of 2004.

      Declines in oil and gas production can be expected in future periods due
to natural depletion. Given the small number of producing wells owned by the
Partnership, and the fact that offshore wells tend to decline at a faster rate
than onshore wells, the Partnership's future production will be subject to more
volatility than those companies with greater reserves and longer-lived
properties.

OPERATING EXPENSES

      The Partnership's depreciation, depletion and amortization (DD&A) rate,
expressed as a percentage of oil and gas sales, was approximately 21 percent
during the first quarter of 2004 compared to 23 percent during the same period
in 2003. The decline in rate in 2004 reflected higher prices in the current year
and reserve additions from recompletions in 2003. During the first quarter, the
Partnership recognized $11,922 of accretion expense on the asset retirement
obligation.

                                       5

<PAGE>

      Lease operating expense (LOE) in the first quarter of 2004 decreased 23
percent from the first quarter of 2003 as a result of lower workover and repair
costs in 2004. Administrative expense declined slightly from a year ago to
$102,000 for the quarter.

CASH FLOW, LIQUIDITY AND CAPITAL RESOURCES

CAPITAL RESOURCES AND LIQUIDITY

      The Partnership's primary capital resource is net cash provided by
operating activities, which totaled $2.7 million for the first three months of
2004. Net cash provided by operating activities in the quarter was up 41 percent
from a year ago as a result of increases in oil prices, higher oil and natural
gas production, and reduced operating costs. Future cash flows will be
influenced by fluctuations in product prices, production levels and operating
costs.

      The Partnership's future financial condition, results of operations and
cash from operating activities will largely depend upon prices received for its
oil and natural gas production. A substantial portion of the Partnership's
production is sold under market-sensitive contracts. Prices for oil and natural
gas are subject to fluctuations in response to changes in supply, market
uncertainty and a variety of factors beyond the Partnership's control. These
factors include worldwide political instability (especially in the Middle East),
the foreign supply of oil and natural gas, the price of foreign imports, the
level of consumer demand, and the price and availability of alternative fuels.
With natural gas accounting for 62 percent of the Partnership's first quarter
2004 production and 62 percent of total proved reserves at December 31, 2003, on
an energy equivalent basis, the Partnership is affected more by fluctuations in
natural gas prices than in oil prices.

      The Partnership's oil and gas reserves and production will also
significantly impact future results of operations and cash from operating
activities. The Partnership's production is subject to fluctuations in response
to remaining quantities of oil and gas reserves, weather, pipeline capacity,
consumer demand, mechanical performance and workover, recompletion and drilling
activities. Declines in oil and gas production can be expected in future years
as a result of normal depletion and the Partnership not participating in
acquisition or exploration activities. Based on production estimates from
independent engineers and current market conditions, the Partnership expects it
will be able to meet its liquidity needs for routine operations in the
foreseeable future. The Partnership will reduce capital expenditures and
distributions to partners as cash from operating activities decline.

      In the event that future short-term operating cash requirements are
greater than the Partnership's financial resources, the Partnership may seek
short-term, interest-bearing advances from the Managing Partner as needed. The
Managing Partner, however, is not obligated to make loans to the Partnership.

      On an ongoing basis, the Partnership reviews the possible sale of lower
value properties prior to incurring associated dismantlement and abandonment
costs.

CAPITAL COMMITMENTS

      The Partnership's primary needs for cash are for operating expenses,
drilling and recompletion expenditures, future dismantlement and abandonment
costs, distributions to Investing Partners, and the purchase of Units offered by
Investing Partners under the right of presentment. The Partnership had no
outstanding debt or lease commitments at March 31, 2004.

      During the first three months of 2004, the Partnership invested $.4
million in oil and gas properties as the Partnership participated in
recompletions at South Timbalier Block 295 and Ship Shoal 258. The Partnership
is participating in drilling the Ship Shoal 258 JB-6 well which was in-progress
at March 31, 2004. Based on information supplied by the operators of the
properties, the Partnership anticipates capital expenditures of approximately
$1.8 million for the remainder of 2004, primarily for drilling at Ship Shoal
258/259. The Partnership currently plans to participate in drilling six wells in
the field in 2004. Such estimates may change based on realized prices, drilling
results or changes by the operator to the development plan.

      On March 17, 2004, the Partnership paid distributions to Investing
Partners totaling $2.1 million, or $2,000 per Investing Partner unit. The
Partnership made a cash distribution to Investing Partners during the first
quarter of 2003 of $500 per Investing Partner Unit. The amount of future
distributions will be dependent on actual and expected production levels,
realized and expected oil and gas prices, expected drilling and recompletion

                                       6

<PAGE>

expenditures, and prudent cash reserves for future dismantlement and abandonment
costs that will be incurred after the Partnership's reserves are depleted.

      As provided in the Amended Partnership Agreement, a first right of
presentment offer for 2004 of $11,518 per Unit was offered to Investing Partners
in April 2004, based on a valuation date of December 31, 2003. The Partnership
is not in a position to predict how many Units will be presented for repurchase
under the April 2004 offer and cannot, at this time, determine if the
Partnership will have sufficient funds available to repurchase any Units. The
Investing Partners have until May 21, 2004 to offer their Units under the
current right of presentment. The Partnership has no obligation to purchase any
Units presented to the extent it determines that it has insufficient funds for
such purchases. The Amended Partnership Agreement contains limitations on the
number of Units that the Partnership can repurchase, including a limit of 10
percent of the outstanding Units on an annual basis.

ITEM 3 - QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

      The Partnership's major market risk exposure is in the pricing applicable
to its oil and gas production. Realized pricing is primarily driven by the
prevailing worldwide price for crude oil and spot prices applicable to its
natural gas production. Prices received for oil and gas production have been and
remain volatile and unpredictable. The Partnership has not used derivative
financial instruments or otherwise engaged in hedging activities during 2003 or
the first three months of 2004.

      The information set forth under "Commodity Risk" in Item 7A of the
Partnership's Form 10-K for the year ended December 31, 2003, is incorporated by
reference. Information about market risks for the current quarter is not
materially different.

ITEM 4 - CONTROLS AND PROCEDURES

      G. Steven Farris, the Managing Partner's President, Chief Executive
Officer and Chief Operating Officer, and Roger B. Plank, the Managing Partner's
Executive Vice President and Chief Financial Officer, evaluated the
effectiveness of the Partnership's disclosure controls and procedures as of the
end of the period covered by this report. Based on that evaluation and as of the
date of that evaluation, these officers concluded that the Partnership's
disclosure controls to be effective, providing effective means to insure that
information it is required to disclose under applicable laws and regulations is
recorded, processed, summarized and reported in a timely manner. Also, no
significant changes were made in the Partnership's internal controls over
financial reporting during the fiscal quarter ending March 31, 2004 that have
materially affected, or are reasonably likely to materially affect, the
Partnership's internal control over financial reporting.

FORWARD-LOOKING STATEMENTS AND RISK

      Certain statements in this report, including statements of the future
plans, objectives, and expected performance of the Partnership, are
forward-looking statements that are dependent on certain events, risks and
uncertainties that may be outside the Partnership's control, and which could
cause actual results to differ materially from those anticipated. Some of these
include, but are not limited to, the market prices of oil and gas, economic and
competitive conditions, inflation rates, legislative and regulatory changes,
financial market conditions, political and economic uncertainties of foreign
governments, future business decisions, and other uncertainties, all of which
are difficult to predict.

      There are numerous uncertainties inherent in estimating quantities of
proved oil and gas reserves and in projecting future rates of production and
timing of development expenditures. The total amount or timing of actual future
production may vary significantly from reserves and production estimates. The
drilling of exploratory wells can involve significant risks, including those
related to timing, success rates and cost overruns. Lease and rig availability,
complex geology and other factors can affect these risks. Fluctuations in oil
and gas prices, or a prolonged period of low prices, may substantially adversely
affect the Partnership's financial position, results of operations and cash
flows.

                                       7

<PAGE>

                           PART II - OTHER INFORMATION

ITEM 1.   LEGAL PROCEEDINGS

          None.

ITEM 2.   CHANGES IN SECURITIES, USE OF PROCEEDS AND ISSUER PURCHASES OF EQUITY
          SECURITIES

          None.

ITEM 3.   DEFAULTS UPON SENIOR SECURITIES

          None.

ITEM 4.   SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

          None.

ITEM 5.   OTHER INFORMATION

          None.

ITEM 6.   EXHIBITS AND REPORTS ON FORM 8-K

          a.    Exhibits

                31.1 - Certification of Chief Executive Officer

                31.2 - Certification of Chief Financial Officer

                32.1 - Certification of Chief Executive Officer and Chief
                       Financial Officer

          b.    Reports filed on Form 8-K - None.

                                       8

<PAGE>

                                   SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange
Act of 1934, the registrant has duly caused this report to be signed on its
behalf by the undersigned thereunto duly authorized.

                                      APACHE OFFSHORE INVESTMENT PARTNERSHIP
                                      By: Apache Corporation, General Partner

Dated: May 7, 2004                    /s/ Roger B. Plank
                                      ------------------------------------------
                                      Roger B. Plank
                                      Executive Vice President and Chief
                                      Financial Officer

Dated: May 7, 2004                    /s/ Thomas L. Mitchell
                                      ------------------------------------------
                                      Thomas L. Mitchell
                                      Vice President and Controller
                                      (Chief Accounting Officer)

<PAGE>

                               INDEX TO EXHIBITS

      31.1  - Certification of Chief Executive Officer

      31.2  - Certification of Chief Financial Officer

      32.1  - Certification of Chief Executive Officer and Chief Financial
              Officer

                                       8