<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 September 30, 2005

                                       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)

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

<TABLE>
<S>                                                             <C>
     Suite 100, One Post Oak Central                            77056-4400
  2000 Post Oak Boulevard, Houston, TX                          (Zip Code)
(Address of Principal Executive Offices)
</TABLE>

       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 INCOME
                                   (UNAUDITED)

<TABLE>
<CAPTION>
                                                  FOR THE QUARTER         FOR THE NINE MONTHS
                                                ENDED SEPTEMBER 30,       ENDED SEPTEMBER 30,
                                              -----------------------   -----------------------
                                                 2005         2004         2005         2004
                                              ----------   ----------   ----------   ----------
<S>                                           <C>          <C>          <C>          <C>
REVENUES:
   Oil and gas sales                          $3,113,863   $3,440,706   $9,839,038   $9,865,405
   Interest income                                40,043       13,757       79,678       26,006
                                              ----------   ----------   ----------   ----------
                                               3,153,906    3,454,463    9,918,716    9,891,411
                                              ----------   ----------   ----------   ----------
EXPENSES:
   Depreciation, depletion and amortization      448,058      766,845    1,463,283    2,140,142
   Asset retirement obligation accretion          10,480       12,272       35,038       36,290
   Lease operating costs                         344,508      183,885      942,608      609,656
   Gathering and transportation expense           34,155       33,376      118,530       95,496
   Administrative                                107,000      102,000      321,000      306,000
                                              ----------   ----------   ----------   ----------
                                                 944,201    1,098,378    2,880,459    3,187,584
                                              ----------   ----------   ----------   ----------
NET INCOME                                    $2,209,705   $2,356,085   $7,038,257   $6,703,827
                                              ==========   ==========   ==========   ==========
NET INCOME ALLOCATED TO:
   Managing Partner                           $  514,513   $  603,772   $1,653,873   $1,712,934
   Investing Partners                          1,695,192    1,752,313    5,384,384    4,990,893
                                              ----------   ----------   ----------   ----------
                                              $2,209,705   $2,356,085   $7,038,257   $6,703,827
                                              ==========   ==========   ==========   ==========
NET INCOME PER INVESTING PARTNER UNIT         $    1,606   $    1,657   $    5,101   $    4,712
                                              ==========   ==========   ==========   ==========
WEIGHTED AVERAGE INVESTING PARTNER
   UNITS OUTSTANDING                             1,055.4      1,057.2      1,055.5      1,059.2
                                              ==========   ==========   ==========   ==========
</TABLE>

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


                                        1

<PAGE>

                     APACHE OFFSHORE INVESTMENT PARTNERSHIP
                             STATEMENT OF CASH FLOWS
                                   (UNAUDITED)

<TABLE>
<CAPTION>
                                                                 FOR THE NINE MONTHS ENDED
                                                                       SEPTEMBER 30,
                                                                 -----------   -----------
                                                                     2005          2004
                                                                 -----------   -----------
<S>                                                              <C>           <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
   Net income                                                    $ 7,038,257   $ 6,703,827
   Adjustments to reconcile net income to net cash
      provided by operating activities:
         Depreciation, depletion and amortization                  1,463,283     2,140,142
         Asset retirement obligation accretion                        35,038        36,290
         Dismantlement and abandonment cost                               --      (187,160)
         Changes in operating assets and liabilities:
            (Increase) decrease in accrued revenues receivable       (55,531)       31,144
            Increase (decrease) in accrued operating expenses         14,825         3,932
            (Increase) decrease in payable to/receivable from
               Apache Corporation                                    393,918       (82,198)
                                                                 -----------   -----------
         Net cash provided by operating activities                 8,889,790     8,645,977
                                                                 -----------   -----------

CASH FLOWS FROM INVESTING ACTIVITIES:
   Additions to oil and gas properties                              (492,363)   (1,706,329)
   Proceeds from sale of oil and gas properties                      136,252            --
                                                                 -----------   -----------
         Net cash used in investing activities                      (356,111)   (1,706,329)
                                                                 -----------   -----------

CASH FLOWS FROM FINANCING ACTIVITIES:
   Repurchase of Partnership Units                                    (3,193)      (41,321)
   Distributions to Investing Partners                            (4,222,585)   (2,121,466)
   Distributions to Managing Partner                              (1,701,939)   (1,745,962)
                                                                 -----------   -----------
         Net cash used in financing activities                    (5,927,717)   (3,908,749)
                                                                 -----------   -----------
NET INCREASE IN CASH AND CASH EQUIVALENTS                          2,605,962     3,030,899
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR                       3,333,640     2,271,495
                                                                 -----------   -----------
CASH AND CASH EQUIVALENTS, END OF PERIOD                         $ 5,939,602   $ 5,302,394
                                                                 ===========   ===========
</TABLE>

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


                                        2

<PAGE>

                     APACHE OFFSHORE INVESTMENT PARTNERSHIP
                                  BALANCE SHEET
                                   (UNAUDITED)



<TABLE>
<CAPTION>
                                                                              SEPTEMBER 30,    DECEMBER 31,
                                                                                   2005            2004
                                                                              -------------   -------------
<S>                                                                           <C>             <C>
                                   ASSETS

CURRENT ASSETS:
   Cash and cash equivalents                                                  $   5,939,602   $   3,333,640
   Accrued revenues receivable                                                    1,020,852         965,321
   Receivable from Apache Corporation                                                    --         165,474
                                                                              -------------   -------------
                                                                                  6,960,454       4,464,435
                                                                              -------------   -------------
OIL AND GAS PROPERTIES, on the basis of full cost accounting:
   Proved properties                                                            184,616,609     184,065,602
   Less - Accumulated depreciation, depletion and amortization                 (177,778,500)   (176,315,217)
                                                                              -------------   -------------
                                                                                  6,838,109       7,750,385
                                                                              -------------   -------------
                                                                              $  13,798,563   $  12,214,820
                                                                              =============   =============
                     LIABILITIES AND PARTNERS' CAPITAL

CURRENT LIABILITIES:
   Distributions payable                                                      $   5,277,032   $          --
   Accrued exploration and development                                              363,229              --
   Accrued operating expenses                                                        78,594          63,769
   Payable to Apache Corporation                                                    228,444              --
                                                                              -------------   -------------
                                                                                  5,947,299          63,769
                                                                              -------------   -------------
ASSET RETIREMENT OBLIGATION                                                         724,912         858,207
                                                                              -------------   -------------
PARTNERS' CAPITAL:
   Managing Partner                                                                 159,555         207,621
   Investing Partners (1,055.4 and 1,055.7 units outstanding, respectively)       6,966,797      11,085,223
                                                                              -------------   -------------
                                                                                  7,126,352      11,292,844
                                                                              -------------   -------------
                                                                              $  13,798,563   $  12,214,820
                                                                              =============   =============
</TABLE>


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


                                        3

<PAGE>

                     APACHE OFFSHORE INVESTMENT PARTNERSHIP
                          NOTES TO 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/PAYABLE TO APACHE CORPORATION

     The receivable from/payable to 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 paid by Apache to the Partnership
or 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 2005 of $12,418
per Unit, plus interest to the date of payment, was made to Investing Partners
in April 2005, based on a valuation date of December 31, 2004. As a result, the
Partnership purchased .25 Units in May 2005 for a total of $3,193. A second
right of presentment offer for 2005 of $9,337 per Unit, plus interest to the
date of payment, was made to Investing Partners on October 28, 2005, based on a
valuation date of June 30, 2005. The Investing Partners have until the close of
business on November 28, 2005 to present their Units for repurchase by the
Partnership. The Partnership will determine by December 15, 2005, whether or not
to accept each Unit offered during this election period.

     The Partnership is not in a position to predict how many Units will be
presented for repurchase during the fourth quarter of 2005 and cannot, at this
time, determine if the Partnership will have sufficient funds available to
repurchase any Units. 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

     The following table describes changes to the Partnership's asset retirement
obligation liability for the nine months ended September 30, 2005:

<TABLE>
<S>                                              <C>
Balance at December 31, 2004                     $ 858,207
Accretion expense                                   35,038
Reduction in liability from sale of properties    (168,333)
                                                 ---------
Balance at September 30, 2005                    $ 724,912
                                                 =========
</TABLE>


                                        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 earned $2.2 million during the third quarter of 2005, six
percent less than the net income reported in the third quarter of 2004. Net
income per Investing Partner Unit decreased from $1,657 in the third quarter of
2004 to $1,606 in the current quarter. Lower oil and gas production and higher
operating costs more than offset the impact of higher prices in the current
period. Downtime for hurricanes which battered the U.S. Gulf Coast during the
quarter contributed to a 40 percent decline in equivalent production from a year
ago. By the end of the first week in October, the Partnership had restored
substantially all of its production impacted by hurricanes. While operators
continue to inspect platforms and equipment, the Partnership appears to have
avoided major damage to its facilities.

     Net income for the first nine months of 2005, totaled $7.0 million or
$5,101 per Investing Partner Unit. Net income for the same period in 2004
totaled $6.7 million or $4,712 per Investing Partner Unit. Higher oil and gas
prices during the first nine months of 2005 drove the five percent increase in
net income from the comparable period in 2004.

     Total revenues for the third quarter decreased $.3 million, or nine
percent, from a year ago as a result of lower production. For the nine months
ending September 30, 2005, total revenue was essentially even with a year ago.
Interest income for the third quarter and first nine months of 2005 were
approximately three times the amounts in 2004 on higher average cash balances
and higher interest rates.

     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 QUARTER ENDED SEPTEMBER 30,   FOR THE NINE MONTHS ENDED SEPTEMBER 30,
                                 -----------------------------------   ---------------------------------------
                                                        INCREASE                                INCREASE
                                      2005     2004    (DECREASE)             2005     2004    (DECREASE)
                                     ------   ------   ----------            ------   ------   ----------
<S>                              <C>          <C>      <C>             <C>            <C>      <C>
Gas volume - Mcf per day              2,608    3,891      (33%)               3,146    3,761     (16%)
Average gas price - per Mcf          $ 8.94   $ 5.85       53%               $ 7.39   $ 5.93      25%
Oil volume - barrels per day            161      286      (44%)                 211      312     (32%)
Average oil price - per barrel       $60.68   $42.83       42%               $52.36   $38.45      36%
NGL volume - barrels per day             25       93      (73%)                  54       69     (22%)
Average NGL price - per barrel       $31.17   $25.71       21%               $32.33   $24.77      31%
</TABLE>

OIL AND GAS SALES

     Natural gas production revenues for the third quarter of 2005 totaled $2.1
million, up two percent from the third quarter of 2004 as higher prices more
than offset the impact of lower production. The Partnership's average realized
natural gas price for the third quarter of 2005 increased 53 percent compared to
the year-earlier period. The $3.09 per Mcf increase in gas price from a year ago
positively impacted sales by approximately $1.1 million. Natural gas volumes on
a daily basis decreased 33 percent from a year ago as a result of
hurricane-related downtime and natural depletion. The Partnership experienced up
to 22 days of hurricane-related downtime during the third quarter, primarily for
Hurricane Katrina in August and Hurricane Rita in September. By the end of the
first week in October, the Partnership had restored substantially all of its
production impacted by hurricanes. The Partnership successfully completed the
Ship Shoal 258 JA-9 well as a producer in late August, but the well had minimal
impact on the quarter with the downtime for hurricanes.

     The Partnership's crude oil production revenues for the third quarter of
2005 totaled $.9 million, a 20 percent decrease from the third quarter of 2004.
Oil production for the quarter declined 44 percent from the comparable period in
2004 as a result of natural depletion and hurricane-related downtime. A $17.85
per barrel, or 42 percent, increase in the Partnership's average realized oil
price favorably impacted oil revenues by $.5 million.

     Gas sales for the first nine months of 2005 of $6.3 million increased four
percent, when compared to the same period in 2004. The Partnership's average
realized gas prices increased $1.46 per Mcf, when compared with the first


                                        5

<PAGE>

nine months of 2004. Daily gas production for the first nine months of 2005
decreased 16 percent when compared to the same period in 2004. Declines at South
Timbalier 295 and Matagorda 681/682 more than offset production added through
drilling at Ship Shoal 258/259 in 2004 and 2005.

     For the nine months ended September 30, 2005, oil sales decreased eight
percent from a year ago to $3.0 million. The Partnership's oil sales revenues
were favorably impacted by an 36 percent increase in the average realized oil
price. Daily oil production declined 32 percent from a year ago as a result of
natural depletion and downtime for weather.

     The Partnership sold an average of 54 barrels per day of natural gas
liquids from processing gas during the first nine months of 2005, a 22 percent
decrease over the comparable period in 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 their natural depletion, 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 14 percent
during the third quarter of 2005 compared to 22 percent during the same period
in 2004. This decline in rate reflected the impact of higher oil and gas prices
in the current year, reserves added from drilling in 2004 and the sale of the
Partnership's interest in South Pass 83 as discussed under Capital Resources and
Liquidity. The Partnership recognized $10,480 of accretion expense on the asset
retirement obligation during the third quarter of 2005 and $35,038 for the first
nine months of 2005, down slightly from the comparable periods in 2004 as a
result of the sale of the South Pass 83 field.

     Lease operating expense (LOE) in the third quarter of 2005 was $161,000
higher than the third quarter of 2004, reflecting workover operations on the
North Padre Island 976 A-3 and South Timbalier 295 A-18 wells, and maintenance
on the North Padre Island platform. During the first nine months of 2005, LOE
totaled $.9 million, up 55 percent from the same period in 2004 on higher repair
and maintenance costs and workover costs.

     Gathering and transportation costs include amounts paid by the Partnership
to third parties to transport oil and gas to a purchaser-specified delivery
point. Such costs vary based on the volume and distance shipped, and the fee
charged by the transporter, which may be price sensitive. The transportation
cost may also vary from period to period based on marketing and delivery options
utilized by the Partnership to realize the highest net price (gross price less
transportation) for either oil or gas. Gathering and transportation costs during
the third quarter and first nine months of 2005 were up slightly from the
comparable periods in 2005.

CAPITAL RESOURCES AND LIQUIDITY

     The Partnership's primary capital resource is net cash provided by
operating activities, which totaled $8.9 million for the first nine months of
2005. Net cash provided by operating activities in 2005 was three percent above
the $8.6 million reported a year ago, reflecting increases in oil and gas prices
from 2004. 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 70 percent of the Partnership's production for
the first nine months of 2005 and 62 percent of total proved reserves at
December 31, 2004, 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


                                        6

<PAGE>

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 declines.

     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. However, the
Managing Partner 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
cost. In June 2005, the Partnership sold its interest in the South Pass 83 field
to a third party for $136,252, subject to normal post closing adjustments. The
purchaser also assumed all dismantlement and abandonment obligations for the
property. The South Pass 83 field had insignificant levels of production at the
time of the sale and the divestiture is not expected to materially impact future
operating income.

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 September 30, 2005. The Partnership did
not have any contractual obligations as of September 30, 2005, other than the
liability for dismantlement and abandonment costs of its oil and gas properties.
The Partnership has recorded a separate liability for the fair value of its
asset retirement obligations.

     The Partnership participated in drilling the Ship Shoal 259 JA-9 and JA-10
wells during the third quarter of 2005. The Partnership's oil and gas property
expenditures during the first half were primarily for seismic costs. The JA-9
well was completed as a producing well in late August, while the JA-10 well was
still being evaluated at the end of the third quarter.

     Based on information supplied by the operators of the properties, the
Partnership anticipates capital expenditures for the remainder of 2005 of
approximately $.5 million to participate in drilling in the Ship Shoal 258 JB-7
well during the fourth quarter and complete the Ship Shoal JA-10 well. Such
estimates may change based on realized prices, drilling results or changes by
the operator to the development plan.

     On March 17, 2005, the Partnership paid distributions to Investing Partners
totaling $4.2 million, or $4,000 per Investing Partner unit. The Partnership
made a cash distribution to Investing Partners during the first nine months of
2004 of $2,000 per Investing Partner Unit. The Partnership declared a
distribution of $5,000 per Investing Partner Unit on September 12, 2005, that
was payable to Unitholders on October 14, 2005. 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
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 2005 of $12,418 per Unit was offered to Investing Partners
in April 2005, based on a valuation date of December 31, 2004. As a result, the
Partnership purchased .25 Units in May 2005 for a total of $3,193. A second
right of presentment offer for 2005 of $9,337 per Unit, plus interest to the
date of payment, was made to Investing Partners on October 28, 2005, based on a
valuation date of June 30, 2005. The Investing Partners have until the close of
business on November 28, 2005 to present their Units for repurchase by the
Partnership. The Partnership will determine by December 15, 2005, whether or not
to accept each Unit offered during this election period.

     The Partnership is not in a position to predict how many Units will be
presented for repurchase during the fourth quarter of 2005 and cannot, at this
time, determine if the Partnership will have sufficient funds available to
repurchase any Units. 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.


                                        7

<PAGE>

ITEM 3 - QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

COMMODITY 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 2004 or
the first nine months of 2005.

     The information set forth under "Commodity Risk" in Item 7A of the
Partnership's Form 10-K for the year ended December 31, 2004, is incorporated by
reference. Information about market risks for the current quarter is not
materially different.

GOVERNMENTAL RISK

     The Partnership's operations have been, and at times in the future may be,
affected by political developments and by federal, state and local laws and
regulations impacting production levels, taxes, environmental requirements and
other assessments including a potential windfall profits tax.

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 September 30, 2005 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.


                                        8

<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.


                                        9

<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: November 8, 2005                 /s/ Roger B. Plank
                                        ----------------------------------------
                                        Roger B. Plank
                                        Executive Vice President and Chief
                                        Financial Officer


Dated: November 8, 2005                 /s/ Thomas L. Mitchell
                                        ----------------------------------------
                                        Thomas L. Mitchell
                                        Vice President and Controller
                                        (Chief Accounting Officer)

<PAGE>

INDEX TO EXHIBITS

<TABLE>
<CAPTION>
Exhibit
Number    Description of Exhibit
-------   ----------------------
<S>       <C>
  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
</TABLE>