<PAGE>
 
    AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MARCH 21, 1996

                                                      Registration No. 33-
===============================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                                        
                                    FORM S-3
            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                                  ----------
                                        
                             PLAINS RESOURCES INC.
             (Exact name of registrant as specified in its charter)

           DELAWARE                                   13-2898764
(State or other jurisdiction of         (I.R.S. Employer Identification No.)
 incorporation or organization)

                               1600 SMITH STREET
                              HOUSTON, TEXAS 77002
                                 (713) 654-1414
  (Address, including zip code, and telephone number, including area code, of
                   registrant's principal executive offices)

                                  ----------                                

                              MICHAEL R. PATTERSON
                       VICE PRESIDENT AND GENERAL COUNSEL
                             PLAINS RESOURCES INC.
                               1600 SMITH STREET
                              HOUSTON, TEXAS 77002
                                 (713) 654-1414
 (Name, address, including zip code, and telephone number, including area code,
                             of agent for service)

                                  ----------
                                        
                                    COPY TO:
                                 JOHN A. WATSON
                          Fulbright & Jaworski L.L.P.
                           1301 McKinney, Suite 5100
                           Houston, Texas 77010-3095
                                 (713) 651-5151

                                  ----------
                                        
  APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:  As soon as
practicable after the effective date of this Registration Statement.

  If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box: [ ]

  If any of the securities being registered on this Form are to be offered on a
delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box. [x]

  If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering. [ ]

  If this Form is a post-effective amendment filed pursuant to Rule 462(c) under
the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [ ]

  If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. [ ]

                                  ----------

                        CALCULATION OF REGISTRATION FEE

<TABLE> 
<CAPTION> 
==================================================================================================== 
                                                       PROPOSED         PROPOSED
                                                       MAXIMUM          MAXIMUM          AMOUNT OF
  TITLE OF EACH CLASS OF           AMOUNT TO        OFFERING PRICE      AGGREGATE      REGISTRATION
SECURITIES TO BE REGISTERED      BE REGISTERED        PER SHARE*     OFFERING PRICE*       FEE
----------------------------------------------------------------------------------------------------
<S>                            <C>                  <C>              <C>               <C> 
Common Stock, par value $.10
 per share...................   798,143 shares         $8.375          $6,684,448         $2,305
==================================================================================================== 
</TABLE> 
* Estimated solely for the purpose of calculating the registration fee and based
  upon the average of the high and low sales prices of Common Stock as reported
  by the American Stock Exchange on March 18, 1996, which was $8-3/8.

  THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES
AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE
A FURTHER AMENDMENT THAT SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT
SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF THE
SECURITIES ACT OF 1933 OR UNTIL THIS REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE SECURITIES AND EXCHANGE COMMISSION, ACTING
PURSUANT TO SAID SECTION 8(A), MAY DETERMINE.
================================================================================
<PAGE>
 
*******************************************************************************
* Information contained herein is subject to completion or amendment. A       *
* registration statement relating to these securities has been filed with the *
* Securities and Exchange Commission. These securities may not be sold nor    *
* may offers to buy be accepted prior to the time the registration statement  *
* becomes effective. This prospectus shall not constitute an offer to sell    *
* or the solicitation of an offer to buy nor shall there be any sale of these *
* securities in any State in which such offer, solicitation or sale would be  *
* unlawful prior to registration or qualification under the securities laws   *
* of any State.                                                               *
*******************************************************************************

                  SUBJECT TO COMPLETION, DATED MARCH 21, 1996

P R O S P E C T U S

                    [LOGO OF PLAINS RESOURCES APPEARS HERE]

                                 798,143 SHARES
                                  COMMON STOCK

                                  ----------

  This Prospectus has been prepared for use in connection with the proposed sale
by the holders thereof (the "Selling Stockholders") of an aggregate of 798,143
shares (the "Shares") of common stock, par value $.10 per share (the "Common
Stock"), of Plains Resources Inc. (the "Company").   The Shares may be sold from
time to time by or for the account of the Selling Stockholders in the over-the-
counter market, on the American Stock Exchange ("AMEX") or otherwise at prices
and on terms then prevailing or at prices related to the then current market
price, directly or through agents designated from time to time, or through
dealers or underwriters to be designated or in negotiated transactions.  The
Shares may be sold by any one or more of the following methods:  (a) a block
trade (which may involve crosses) in which the broker or dealer so engaged will
attempt to sell the securities as agent but may position and resell a portion of
the block as principal to facilitate the transaction; (b) purchases by a broker
or dealer as principal and resale by such broker or dealer for its account
pursuant to this Prospectus; (c) exchange distributions and/or secondary
distributions in accordance with the rules of the AMEX; (d) ordinary brokerage
transactions and transactions in which the broker solicits purchasers; (e)
through the writing of options on Shares (whether such options are listed on an
options exchange or otherwise); or (f) privately negotiated transactions.  To
the extent required by applicable law, the specific Shares to be sold, the names
of the Selling Stockholders, the respective purchase prices and public offering
prices, the names of any such agent, dealer or underwriter and any applicable
commissions or discounts with respect to a particular offer will be set forth in
an accompanying Prospectus Supplement.  See "Plan of Distribution."

  The Common Stock is traded on the AMEX under the symbol "PLX."  On March 19,
1996, the last reported sale price for the Common Stock on the American Stock
Exchange was $8-3/8 per share.

  The Company will receive no portion of the proceeds of the sale of the Shares
offered hereby and will bear certain of the expenses incident to their
registration.  See "Plan of Distribution" and "Selling Stockholders."

  The Shares have not been registered for sale under the securities laws of any
state or jurisdiction as of the date of this Prospectus.  Brokers or dealers
effecting transactions in the Shares should confirm the registration thereof
under the securities laws of the states in which such transactions occur, or the
existence of any exemption from registration.

                                  ----------

        PROSPECTIVE INVESTORS SHOULD CAREFULLY CONSIDER THE MATTERS SET
                    FORTH UNDER THE CAPTION "RISK FACTORS."

                                  ----------
                                        
  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
    EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECU-
       RITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION
         PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS.  ANY
             REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

             , 1996
<PAGE>
 
                             AVAILABLE INFORMATION

  The Company has filed with the Securities and Exchange Commission (the
"Commission") in Washington, D.C., a Registration Statement on Form S-3 (the
"Registration Statement") under the Securities Act of 1933, as amended (the
"Securities Act"), with respect to the securities offered by this Prospectus.
Certain of the information contained in the Registration Statement is omitted
from this Prospectus, and reference is hereby made to the Registration Statement
and exhibits and schedules relating thereto for further information with respect
to the Company and the securities offered by this Prospectus.  The Company is
subject to the informational requirements of the Securities Exchange Act of
1934, as amended (the "Exchange Act"), and, in accordance therewith, files
reports, proxy statements and other information with the Commission.  Such
reports, proxy statements and other information are available for inspection at,
and copies of such materials may be obtained upon payment of the fees prescribed
therefor by the rules and regulations of the Commission from the Commission at
its principal offices located at Judiciary Plaza, 450 Fifth Street, Room 1024,
Washington, D.C. 20549, and at the Regional Offices of the Commission located at
Northwestern Atrium Center, 500 West Madison Street, Suite 1400, Chicago,
Illinois 60661-2511; and at 7 World Trade Center, Suite 1300, New York, New York
10048.  In addition, the Common Stock of the Company ("Common Stock") is traded
on the American Stock Exchange, and such reports, proxy statements and other
information may be inspected at the offices of the American Stock Exchange,
Inc., 86 Trinity Place, New York, New York 10006.

                       INCORPORATION OF CERTAIN DOCUMENTS

  The Company's Annual Report on Form 10-K for the fiscal year ended December 
31, 1995 (the "Form 10-K"), and the Company's Current Report on Form 8-K filed 
with the Commission on January 4, 1996, as amended by Amendment No. 1 on Form 
8-K/A filed with the Commission on February 21, 1996, are hereby incorporated 
herein by reference.

  The description of the Common Stock, which is contained in a registration 
statement on Form 8-A filed under the Exchange Act, including any amendment or 
reports filed for the purpose of updating such description, is incorporated 
herein by reference.

  All documents filed by the Company pursuant to Section 13(a), 13(c), 14 or 
15(d) of the Exchange Act, after the date of this Prospectus and prior to the 
termination of the Registration Statement of which this Prospectus is a part 
with respect to registration of the Shares, shall be deemed to be incorporated 
by reference in this Prospectus and be a part hereof from the date of filing of 
such documents. Any statement contained in a document incorporated or deemed to 
be incorporated by reference in this Prospectus shall be deemed to be modified 
or superseded for purposes of this Prospectus to the extent that a statement 
contained in this Prospectus, or in any other subsequently filed document that 
also is or is deemed to be incorporated by reference, modifies or replaces such 
statement.

  The Company undertakes to provide without charge to each person, including any
beneficial owner, to whom a copy of this Prospectus has been delivered, upon 
written or oral request of any such person, a copy of any or all of the 
documents incorporated by reference herein, other than exhibits to such 
documents, unless such exhibits are specifically incorporated by reference into 
the information that this Prospectus incorporates. Written or oral requests for
such copies should be directed to: Plains Resources Inc., 1600 Smith Street,
Houston, Texas 77002, Attention: Investor Relations Department, telephone (713)
654-1414.

                              CERTAIN DEFINITIONS

  As used in this Prospectus, "Mcf" means thousand cubic feet, "BOE" means net 
barrel of oil equivalent and "MCFE" means Mcf of natural gas equivalent. Natural
gas equivalents and crude oil equivalents are determined using the ratio of six 
Mcf of natural gas to one barrel of crude oil, condensate or natural gas 
liquids. "Present Value of Proved Reserves" means the present value (discounted 
at 10%) of estimated future net cash flows (before income taxes) of proved oil 
and natural gas reserves based on product prices in effect on the date of 
determination. "EBITDA" means earnings before interest, taxes, depreciation, 
depletion and amortization.

                                       2
<PAGE>
 
                              PROSPECTUS SUMMARY

  The following summary is qualified in its entirety by the more detailed 
information and financial statements and notes set forth and incorporated by 
reference in this Prospectus. As used herein, the terms "Company" and "Plains" 
means Plains Resources Inc. and its subsidiaries, except as the context may 
otherwise require.

                                  THE COMPANY

  Plains is an independent energy company engaged in the acquisition, 
exploitation, development, exploration and production of oil and natural gas and
the marketing, transportation, terminalling and storage of crude oil. The 
Company's upstream oil and natural gas activities are focused in the Los Angeles
Basin of California (the "LA Basin"), the Sunniland Trend of South Florida (the 
"Sunniland Trend"), the Illinois Basin and the Gulf Coast area of Louisiana. The
Company's downstream marketing activities are concentrated in Oklahoma, where it
owns a two million barrel, above ground crude oil terminalling and storage 
facility, Texas and the Gulf Coast area of Louisiana. Plains' upstream 
operations contributed approximately 90% of the Company's pro forma EBITDA for 
the fiscal year ending December 31, 1995, while the Company's downstream 
activities accounted for the remainder.

  The Company has experienced significant growth over the last four years. The 
Company's proved reserves and Present Value of Proved Reserves have increased 
from 13.7 million BOE and $71.7 million at December 31, 1991 to 101.6 million 
BOE and $366.8 million, respectively, at December 31, 1995. Over the same 
period, the Company's average reserve replacement ratio was 617%, and EBITDA 
increased over 400% from $9.0 million for 1991 to $45.3 million for 1995, pro 
forma for the Illinois Basin Acquisition (as defined below). Such additional 
proved reserves were added at an aggregate average finding and development cost
of $2.38 per BOE ($0.40 per MCFE). During 1995, pro forma for the Illinois Basin
Acquisition, the Company's net production averaged approximately 16,657 BOE per
day and its unit gross profit (gross margin less upstream general and
administrative expense) averaged $6.75 per BOE ($1.13 per MCFE). On a BOE basis,
the Company's proved reserves are approximately 93% crude oil, condensate and
natural gas liquids and 71% of its total proved reserves are classified as
proved developed. The Company's reserve base is long-lived with an average
reserve life, or reserves to production ratio, of 16.7 years (11.9 years based
on proved developed reserves only), pro forma for the Illinois Basin
Acquisition.

  The Company's significant increase in proved reserves, production and cash 
flow from oil and natural gas producing activities is attributable to the 
acquisition and subsequent exploitation of its LA Basin Properties and Sunniland
Trend Properties and the recent acquisition of the Illinois Basin Properties. 
These three core areas are comprised primarily of crude oil properties with 
established production histories and together account for approximately 96% of 
the Company's year-end 1995 proved reserves. The Company believes these 
properties include a significant inventory of lower risk, high return 
exploitation and development projects that are expected to contribute to the 
Company's future growth in production and reserves. During 1996, the Company 
estimates it will spend approximately $40 million on the development and 
exploitation of its LA Basin, Sunniland Trend and Illinois Basin Properties. The
Company operates and owns a 100% working interest in its major fields in each of
these areas, which enables the Company to control the exploitation of such 
properties.

  The Company's marketing effort entails purchasing crude oil from producers and
marketing it to the refining sector. The Company aggregates these volumes at 
major crude oil interchanges and trading locations and is therefore able to 
obtain higher prices for its own production while realizing profits on the 
production purchased from others. The Company owns and operates a two million 
barrel, above ground crude oil storage and terminalling facility in Cushing, 
Oklahoma (the "Cushing Terminal"), the United States' largest inland crude oil 
interchange and trading location. This facility enhances the competitive 
marketing ability of the Company by enabling it to take crude oil from different
sources and make physical delivery of crude oil in Cushing, the NYMEX designated
delivery location. The Company's downstream activities have expanded 
significantly over the last four years, with downstream gross margin (revenues 
less direct

                                       3
<PAGE>
 
expenses of purchases, transportation, storage and terminalling) increasing over
400% from $1.2 million in 1991 to $6.4 million in 1995. Based on additional 
capacity available at the Cushing Terminal, the Company believes it can increase
its downstream gross profit without expending substantial additional capital.

  The Company's upstream and downstream business activities focus on crude oil 
as the primary product. As a result of inefficiencies inherent in the crude oil 
markets and the U.S. pipeline and transportation infrastructure, management 
believes its competitive abilities are enhanced by the alternatives afforded it 
by its proprietary access to the Cushing Terminal. The Company's crude oil 
marketing expertise further provides it with a competitive advantage in 
obtaining higher prices for the Company's existing production and identifying 
potential crude oil price enhancements for properties targeted for acquisition.

BUSINESS STRATEGY

  The Company's business strategy is to increase its proved reserves and cash 
flow by exploiting and producing oil and natural gas from its existing 
properties, acquiring additional underdeveloped oil properties and exploring for
significant new sources of reserves. The Company concentrates its exploitation 
efforts on mature but underdeveloped crude oil producing properties in areas 
that meet the Company's targeted criteria. Generally, such properties were 
previously owned by major integrated oil and gas companies or large independent 
oil and gas companies. Management believes that it has developed a proven record
in acquiring and exploiting underdeveloped crude oil properties where it 
believes substantial reserve additions and cash flow increases can be made 
through improved production practices and recovery techniques and relatively low
risk development drilling. An integral component of the Company's exploitation 
efforts is to increase unit operating margins, and therefore cash flow, by 
reducing unit production expenses and increasing wellhead price realizations. 
The Company also seeks to capitalize on downstream opportunities that complement
its oil producing activities. The Company's marketing of its crude oil 
production takes advantage of the marketing expertise and economies of scale 
attributable to its downstream activities. As part of its business strategy, the
Company periodically evaluates, and from time to time has elected to sell, 
certain of its fully developed producing properties. Such sales enable the 
Company to maintain financial flexibility, control overhead and redeploy the 
sales proceeds to activities that have potentially higher financial returns.

  In order to manage its exposure to commodity price risk, the Company has 
routinely hedged a portion of its crude oil production. For 1996, the Company 
has committed an average of approximately 8,500 Bbls of oil per day to fixed 
price arrangements that expire at various times throughout 1996. Such 
arrangements represent approximately 55% of the Company's pro forma average 
daily oil production for 1995 and partially mitigate the adverse impact of 
potential oil price declines on the Company's operating results.

RECENT ACQUISITION

  On December 22, 1995, the Company acquired all of Marathon Oil Company's 
upstream oil and gas assets in the Illinois Basin (the "Illinois Basin 
Properties"). The acquisition of the Illinois Basin Properties (the "Illinois 
Basin Acquisition") was effective as of November 1, 1995. As a result of such 
acquisition, the Company added approximately 17.3 million barrels of oil to its 
proved reserve base at an aggregate cost of approximately $51.5 million, or an 
average of $2.98 per BOE ($0.50 per MCFE). The Company intends to aggressively 
exploit these properties to evaluate additional reserve potential identified 
during its acquisition analysis. In addition, the Company's exploitation plan 
for the Illinois Basin Properties targets improving the unit gross margin by 
decreasing unit production expenses and increasing price realizations as well as
increasing production volumes by conducting production enhancement activities 
similar to those employed in its LA Basin Properties and Sunniland Trend 
Properties.

                                       4
<PAGE>
 
                              1996 NOTE OFFERING

  On March 19, 1996, the Company sold $150 million in aggregate principal amount
of its 10-1/4% Senior Subordinated Notes due 2006 pursuant to a Rule 144A
private placement. These notes were sold to investors at approximately 99.38% of
the principal amount resulting in a yield to maturity of 10.35%. Proceeds from
the sale of such Notes will be used to redeem all of the Company's 12% Senior
Subordinated Notes due 1999 (the "12% Notes") at 106% of the $100 million
principal amount outstanding plus accrued and unpaid interest thereon. The
remaining proceeds were used to retire a portion of existing bank debt.

                         SALES BY SELLING STOCKHOLDERS

  The Shares to be sold pursuant to this Prospectus are owned by the Selling 
Stockholders. The Company will not receive any of the proceeds from the sale of 
the Shares. See "Selling Stockholders."


                                       5
<PAGE>
 
                                 RISK FACTORS

  Each investor should carefully examine this entire Prospectus and should give 
particular attention to the risk factors set forth below.

SUBSTANTIAL CAPITAL REQUIREMENTS

  The Company makes, and will continue to make, substantial capital expenditures
for the acquisition, exploitation, development, exploration and production of 
oil and gas reserves. Historically, the Company has financed these expenditures
primarily with cash generated by operations, bank borrowings, the offering of
the 12% Notes and the sale of common stock and preferred stock. The Company
intends to make an aggregate of approximately $48 million in capital
expenditures in 1996. The Company believes that it will have sufficient cash
provided by operating activities and borrowings under its revolving credit
facility to fund such planned capital expenditures. If revenues or the Company's
borrowing base decrease as a result of lower oil and gas prices, operating
difficulties or declines in reserves, the Company may have limited ability to
expend the capital necessary to undertake or complete future drilling programs.
There can be no assurance that additional debt or equity financing or cash
generated by operations will be available to meet these requirements.

MARKET CONDITIONS AND VOLATILITY OF OIL AND NATURAL GAS PRICES

  The revenues generated by the Company's operations are highly dependent upon 
the prices of, and demand for, oil and natural gas. Historically, the prices for
oil and natural gas have been volatile and are likely to continue to be volatile
in the future. The price received by the Company for its oil and natural gas 
production and the level of such production are subject to wide fluctuations and
depend on numerous factors beyond the Company's control, including seasonality,
the condition of the United States economy (particularly the manufacturing
sector), foreign imports, political conditions in other oil-producing and
natural gas-producing countries, the actions of the Organization of Petroleum
Exporting Countries and domestic government regulation, legislation and
policies. Decreases in the prices of oil and natural gas have had, and could
have in the future, an adverse effect on the carrying value of the Company's
proved reserves and the Company's revenues, profitability and cash flow.
Although the Company is not currently experiencing any significant involuntary
curtailment of its natural gas production, market, economic and regulatory
factors may in the future materially affect the Company's ability to sell its
natural gas production.

  In order to manage its exposure to price risks in the marketing of its oil and
natural gas, the Company from time to time enters into fixed price delivery 
contracts, financial swaps and oil and natural gas futures contracts as hedging 
devices. To ensure a fixed price for future production, the Company may sell a
futures contract and thereafter either (i) make physical delivery of its product
to comply with such contract or (ii) buy a matching futures contract to unwind
its futures position and sell its production to a customer. These same
techniques are also utilized to manage price risk for certain production
purchased from customers of the Company's marketing subsidiary, Plains Marketing
& Transportation Inc. Such contracts may expose the Company to the risk of
financial loss in certain circumstances, including instances where production is
less than expected, the Company's customers fail to purchase or deliver the
contracted quantities of oil or natural gas, or a sudden, unexpected event
materially impacts oil or natural gas prices. Such contracts may also restrict
the ability of the Company to benefit from unexpected increases in oil and
natural gas prices.

OPERATING HAZARDS AND UNINSURED RISKS

  The Company's operations are subject to all of the risks normally incident to 
the exploration for and the production of oil and natural gas, including 
blowouts, cratering, oil spills and fires, each of which could result in damage 
to or destruction of oil and natural gas wells, production facilities or other 
property, or injury to persons. The relatively deep drilling conducted by the 
Company from time to time involves increased drilling risks of high pressures 
and mechanical difficulties, including stuck pipe, collapsed casing and 
separated cable. The Company's operations in the LA Basin, including 
transportation of crude oil by pipelines within the city of Los Angeles, are 
especially susceptible to damage from earthquakes and involve increased risks of
personal injury, property damage and marketing interruptions because of the 
population density of the area. Although the Company maintains insurance 
coverage considered to be

                                       6
<PAGE>
 
customary in the industry, it is not fully insured against certain of these 
risks, including, in certain instances, earthquake risk in the LA Basin, either 
because such insurance is not available or because of high premium costs. The 
occurrence of a significant event that is not fully insured against could have a
material adverse effect on the Company's financial position.

BUSINESS RISKS

  The Company must continually acquire, explore for, develop or exploit new oil 
and natural gas reserves to replace those produced or sold. Without successful 
drilling, acquisition or exploitation operations, the Company's oil and natural 
gas reserves and revenues will decline. Drilling activities are subject to 
numerous risks, including the risk that no commercially viable oil or natural 
gas production will be obtained. The decision to purchase, explore, exploit or 
develop an interest or property will depend in part on the evaluation of data 
obtained through geophysical and geological analyses and engineering studies, 
the results of which are often inconclusive or subject to varying 
interpretations. The cost of drilling, completing and operating wells is often 
uncertain. Drilling may be curtailed, delayed or canceled as a result of many 
factors, including title problems, weather conditions, compliance with 
government permitting requirements, shortages of or delays in obtaining 
equipment, reductions in product prices or limitations in the market for 
products. The availability of a ready market for the Company's oil and natural
gas production also depends on a number of factors, including the demand for and
supply of oil and natural gas and the proximity of reserves to pipelines or
trucking and terminal facilities. Natural gas wells may be shut in for lack of a
market or due to inadequacy or unavailability of natural gas pipeline or
gathering system capacity.

  Substantially all of the Company's California crude oil production and all of 
the Company's South Florida crude oil production is transported by two pipelines
owned by third parties. The inability of either one of these pipelines to 
provide transportation services to the Company in the future could result in the
involuntary curtailment of a significant portion of the Company's crude oil 
production.

UNCERTAINTIES IN ESTIMATING RESERVES AND FUTURE NET CASH FLOWS

  There are numerous uncertainties inherent in estimating quantities and values 
of proved reserves and in projecting future rates of production and timing of 
development expenditures, including many factors beyond the control of the 
Company. Reserve engineering is a subjective process of estimating the recovery 
from underground accumulations of oil and natural gas that cannot be measured in
an exact manner, and the accuracy of any reserve estimate is a function of the 
quality of available data and of engineering and geological interpretation and 
judgment. Because all reserve estimates are to some degree speculative, the 
quantities of oil and natural gas that are ultimately recovered, production and 
operating costs, the amount and timing of future development expenditures and 
future oil and natural gas sales prices may all differ from those assumed in 
these estimates. In addition, different reserve engineers may make different 
estimates of reserve quantities and cash flows based upon the same available 
data. Therefore, the Present Value of Proved Reserves set forth in this 
Prospectus represents estimates only and should not be construed as the current 
market value of the estimated oil and natural gas reserves attributable to the 
Company's properties. In this regard, the information set forth in this 
Prospectus includes revisions of certain reserve estimates attributable to 
proved properties included in the preceding year's estimates. Such revisions 
reflect additional information from subsequent activities, production history of
the properties involved and any adjustments in the projected economic life of 
such properties resulting from changes in product prices. Any downward revisions
could adversely affect the Company's financial condition, borrowing base under 
its revolving credit facility, future prospects and market value of its 
securities.

LEGAL PROCEEDINGS

  The Company and certain of its officers and directors and a former director 
and officer were named in two class action lawsuits in 1992 and 1993 seeking an 
aggregate of approximately $90 million in compensatory damages and punitive 
damages in an unspecified amount for alleged violations of the federal 
securities laws and state common law arising out of certain alleged 
misrepresentations and omissions in the Company's disclosure regarding its 
onshore natural gas exploration activities. Both of these cases were filed in 
the United States District Court for the Southern District of Texas and are 
captioned respectively, Judith Rubinstein, et al. v. Collins, et al. (C.A. No. 
H-92-1297) and Moroson v. Collins, et al. (C.A. No. H-93-2305). On March 6, 
1996, the Company announced that it had notified the court that a settlement in 
principle had been reached in such cases. Under the terms of the settlement, the
plaintiffs agree to dismiss

                                       7
<PAGE>
 
all claims against the Company and its officers and directors in exchange for a 
cash payment of approximately $6.25 million, including approximately $4.1 
million that is expected to be paid by the Company's insurance carrier, leaving 
approximately $2.1 million to be contributed by the Company. Taking into account
prior costs incurred by the Company to defend these suits, this settlement would
result in a charge to its 1996 first quarter earnings of approximately $4 
million. The settlement is subject to the approval of the court. If the 
settlement is not consummated and if the Company ultimately were required to pay
a substantial portion of the $90 million in compensatory damages sought by the 
plaintiffs, it would have a material adverse effect on the Company.

GOVERNMENT REGULATION

  The Company's business is regulated by certain federal, state and local laws 
and regulations relating to the development, production, marketing, pricing, 
transportation and storage of oil and natural gas. The Company's business is 
also subject to extensive and changing environmental and safety laws and 
regulations governing plugging and abandonment, the discharge of materials into 
the environment or otherwise relating to environmental protections. Certain of 
the Company's properties are located in environmentally sensitive areas that 
require special permits to drill. There can be no assurance that present or 
future regulation will not adversely affect the operations of the Company.

COMPETITION

  The oil and natural gas industry is highly competitive. The Company's 
competitors for the acquisition, exploration, exploitation and development of 
oil and natural gas properties, the purchasing and marketing of oil and the 
crude oil storage and terminalling business, and for capital to finance such 
activities, include companies that have greater financial and personnel 
resources available to them than the Company. The Company's ability to acquire 
additional properties and to discover reserves in the future will be dependent 
upon its ability to evaluate and select suitable properties and to consummate 
transactions in a highly competitive environment.

ISSUANCE OF ADDITIONAL SHARES

  As of March 19, 1996, the Company had 2,693,391 shares of Common Stock 
reserved for issuance upon the exercise of certain warrants and options.

  The Board of Directors, without further action by the stockholders, is 
authorized to issue up to two million shares of the Company's Preferred Stock, 
par value $1.00 per share (the "Preferred Stock"), in one or more series and to 
fix and determine as to any series all the relative rights and preferences of 
shares in such series, including, without limitation, preferences, limitations 
or relative rights with respect to redemption rights, conversion rights, if any,
voting rights, if any, dividend rights and preferences on liquidation. The 
dividend, liquidation and voting rights of any such Preferred Stock issued could
be superior to the rights of the holders of Common Stock.

  The issuance of additional shares of Preferred Stock, or the issuance of 
rights to purchase such shares, could be used to discourage an unsolicited 
acquisition proposal that some, or a majority, of the stockholders might believe
to be in the best interests of the Company or in which stockholders might 
receive a premium for their stock over the then market price of such stock. In 
addition, under certain circumstances, the issuance of Preferred Stock could 
adversely affect the voting power of the holders of the Common Stock.

                                       8
<PAGE>
 
                             SELLING STOCKHOLDERS

  The following table sets forth the beneficial ownership of Common Stock held 
by the Selling Stockholders, immediately prior to and upon completion of this 
offering.

<TABLE> 
<CAPTION> 
                                            Beneficial Ownership                             Beneficial Ownership
                                              Before Offering                                   After Offering
                                            --------------------                             --------------------
                                             Number   Percentage           Shares to          Number   Percentage
         Name                               of Shares  of Class             be Sold          of Shares  of Class
         ----                               --------- ----------           ---------         --------- ----------
<S>                                         <C>       <C>                  <C>               <C>       <C> 
Marathon Oil Company                         537,143      3.3%              537,143             -0-        -0-

Crete Oil Company, Inc.                      171,000      1.1%              171,000             -0-        -0-

Internationale Nederlanden (U.S.)
 Capital Corporation(1)                      190,000      1.2%               90,000           100,000     0.6%
</TABLE> 
----------
(1) Beneficial ownership includes 100,000 shares of Common Stock issuable to
    Internationale Nederlanden (U.S.) Capital Corporation upon the exercise of a
    warrant issued in June 1992, the exercise price of which is $9.50 per share.

  In connection with the Illinois Basin Acquisition, and the financing thereof
in December 1995, the Company issued 537,143 shares of Common Stock to Marathon
Oil Company, 171,000 shares to Crete Oil Company, Inc., and 90,000 shares to
Internationale Nederlanden (U.S.) Capital Corporation ("INCC"). Funding for the
Illinois Acquisition was provided by a $42 million project financing with INCC
and draws under the Company's revolving credit facility with INCC, The First
National Bank of Boston, Den norske Bank, First Interstate Bank of Texas, N.A.
and Texas Commerce Bank National Association.

                             PLAN OF DISTRIBUTION

  The Shares may be sold from time to time by or for the account of the Selling 
Stockholders pursuant to this Prospectus or pursuant to Rule 144 under the 
Securities Act. Sales of Shares pursuant to this Prospectus may be effected in 
the over-the-counter market, on the AMEX or otherwise at prices and on terms 
then prevailing or at prices related to the then current market price (in each 
case as determined by the relevant Selling Stockholder), directly or through 
agents designated from time to time, or through dealers or underwriters to be 
designated or in negotiated transactions. The Shares may be sold by any one or 
more of the following methods: (a) a block trade (which may involve crosses) in 
which the broker or dealer so engaged will attempt to sell the securities as 
agent but may position and resell a portion of the block as principal to 
facilitate the transaction; (b) purchases by a broker or dealer as principal and
resale by such broker or dealer for its account pursuant to this Prospectus; (c)
exchange distributions and/or secondary distributions in accordance with the
rules of the AMEX; (d) ordinary brokerage transactions and transactions in which
the broker solicits purchasers; (e) through the writing of options on Shares
(whether such options are listed on an options exchange or otherwise); or (f)
privately negotiated transactions. To the extent required by applicable law, the
specific Shares to be sold, the names of the Selling Stockholders, the
respective purchase prices and public offering prices, the names of any such
agent, dealer or underwriter and any applicable commissions or discounts with
respect to a particular offer will be set forth in an accompanying Prospectus
Supplement. Each Selling Stockholder may effect such transactions by selling
Shares directly to other purchasers, through agents or through broker-dealers,
and any such agents or broker-dealers may receive compensation in the form of
underwriting discounts, concessions or commissions from such Selling
Stockholder, from purchasers of Shares for whom they act as agents, or from both
sources (and such compensations may be in excess of customary commissions). The
Selling Stockholders and any broker-dealers that participate in the distribution
of the Shares may be deemed to be "underwriters" within the meaning of the
Securities Act in connection with such sales, and any commissions, and any
profit on the resale of Shares, received by the Selling Stockholders and any
such broker-dealers may be deemed to be underwriting discounts and commissions.

                                       9
<PAGE>

  The Company will bear all costs and expenses incurred by it in connection with
the offering and sale of Shares pursuant to this Prospectus, but will not be 
responsible for any commissions, underwriting discounts or similar amounts 
payable in respect of any such sale.

                                 LEGAL OPINION

  The validity of the issuance of the shares of the Common Stock offered hereby 
will be passed upon for the Company by Michael R. Patterson, Esq., its general 
counsel. Mr. Patterson beneficially owns 114,437 shares of Common Stock.

                                    EXPERTS

  The financial statements incorporated in this Prospectus by reference to the 
Annual Report on Form 10-K for the year ended December 31, 1995, have been so 
incorporated in reliance on the report of Price Waterhouse LLP, independent 
accountants, given on authority of said firm as experts in auditing and 
accounting.

  Information relating to the estimated proved reserves of oil and natural gas
and the related estimates of future net revenues and present values thereof for
certain periods, included in the Form 10-K and in the Notes to the Consolidated
Financial Statements of the Company in such Annual Report, has been prepared by
Netherland, Sewell & Associates, Inc., H. J. Gruy and Associates, Inc. and Ryder
Scott Company, independent petroleum engineers, and is incorporated by reference
herein in reliance upon the authority of such firms as experts in petroleum
engineering.


                                       10
<PAGE>
 
================================================================================

NO DEALER, SALESMAN, OR OTHER PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION
OR TO MAKE ANY REPRESENTATIONS NOT CONTAINED IN THIS PROSPECTUS, AND, IF GIVEN
OR MADE, SUCH INFORMATION OR REPRESENTATIONS MUST NOT BE RELIED UPON AS HAVING
BEEN AUTHORIZED BY THE COMPANY OR ANY SELLING STOCKHOLDER OR UNDERWRITER.  THIS
PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL, OR A SOLICITATION OF AN OFFER
TO BUY, THE SECURITIES OFFERED HEREBY IN ANY JURISDICTION WHERE, OR TO ANY
PERSON TO WHOM, IT IS UNLAWFUL TO MAKE SUCH OFFER OR SOLICITATION.  THE DELIVERY
OF THIS PROSPECTUS AT ANY TIME AND ANY SALE MADE HEREUNDER DOES NOT IMPLY THAT
THE INFORMATION CONTAINED OR INCORPORATED BY REFERENCE HEREIN IS CORRECT AS OF
ANY TIME SUBSEQUENT TO ITS DATE.



                               TABLE OF CONTENTS
<TABLE>
<CAPTION>
 
                                        PAGE
                                        ---- 
<S>                                      <C>
Available Information...............      2
Incorporation of Certain Documents..      2
Prospectus Summary..................      3
Risk Factors........................      6
Selling Stockholders................      9
Plan of Distribution................      9
Legal Opinion.......................     10
Experts.............................     10
 
</TABLE>

===============================================================================


=============================================================================== 



                                 798,143 Shares



                    [LOGO OF PLAINS RESOURCES APPEARS HERE]



                                  COMMON STOCK



                              P R O S P E C T U S


                                     , 1996


================================================================================

<PAGE>
 
                                    PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

     The following is a statement of estimated expenses incurred by the Company
in connection with the Common Stock being registered hereby.

<TABLE>
<S>                                                    <C>
Securities and Exchange Commission Registration Fee..   $ 2,305
Legal Fees and Expenses..............................    10,000
Accounting Fees and Expenses.........................       500
Engineering Fees and Expenses........................       500
Miscellaneous........................................     1,695
                                                        -------
  Total..............................................   $15,000
                                                        =======
</TABLE>

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS

  Article Tenth of the Company's Restated Certificate of Incorporation provides
that the Company shall indemnify to the full extent authorized or permitted by
law any person made, or threatened to be made, a party to any action, suit or
proceeding (whether civil, criminal or otherwise) by reason of fact that he, his
testator or intestate, is or was a director or officer of the Company or by
reason of the fact that such director or officer, at the request of the Company,
is or was serving any other corporation, partnership, joint venture, trust,
employee benefit plan or other enterprise, in any capacity.  The rights to
indemnification set forth above are not exclusive of any other rights to which
such person may be entitled under any statute, provision of the Company's
Restated Certificate of Incorporation or bylaws, agreements, vote of
stockholders or disinterested directors or otherwise.

  Additionally, Article VIII of the Company's Bylaws provides for mandatory
indemnification to at least the extent specifically allowed by Section 145 of
the General Corporation Law of the State of Delaware (the "GCL").  The Bylaws
generally follow the language of Section 145 of the GCL, but in addition specify
that any director, officer, employee or agent may apply to any court of
competent jurisdiction in the State of Delaware for indemnification to the
extent otherwise permissible under the Bylaws, notwithstanding any contrary
determination denying indemnification made by the Board, by independent legal
counsel, or by the stockholders, and notwithstanding the absence of any
determination with respect to indemnification.  The Bylaws also specify certain
circumstances in which a finding is required that the person seeking
indemnification acted in good faith, for purposes of determining whether
indemnification is available.  Under the Bylaws, a person shall be deemed to
have acted in good faith and in a manner he reasonably believed to be in or not
opposed to the best interests of the Company, or, with respect to any criminal
action or proceeding, to have had no reasonable cause to believe his conduct was
unlawful, if his action is based on the records or books of account of the
Company or another enterprise, or on information supplied to him by the officers
of the Company or another enterprise in the course of their duties, or on the
advice of legal counsel for the Company  or another enterprise or on information
or records given or reports made to the Company or another enterprise by an
independent certified public accountant or by an appraiser or other expert
selected with reasonable care by the Company or another enterprise.

  Pursuant to Section 145 of the GCL, the Company generally has the power to
indemnify its current and former directors, officers, employees and agents
against expenses and liabilities incurred by them in connection with any suit to
which they are, or are threatened to be made, a party by reason of their serving
in such positions so long as they acted in good faith and in a manner they
reasonably believed to be in, or not opposed to, the best interests of the
Company, and with respect to any criminal action, they had no reasonable cause
to believe their conduct was unlawful.  With respect to suits by or in the right
of the Company, however, indemnification is generally limited to attorneys' fees
and other expenses and is not available if such person is adjudged to be liable
to the Company unless the court determines that indemnification is appropriate.
The statute expressly provides that the power to indemnify authorized thereby is
not exclusive of any rights granted under any bylaw, agreement, vote of
stockholders or disinterested directors, or otherwise.  The Company also has the
power to purchase and maintain insurance for such persons.

                                      II-1

<PAGE>
 
  The above discussion of the Company's Restated Certificate of Incorporation
and Bylaws and Section 145 of the GCL is not intended to be exhaustive and is
qualified in its entirety by each of such documents and such statute.

  The Company has entered into an employment agreement containing
indemnification provisions with Mr. Armstrong, its President and Chief Executive
Officer.  Pursuant to such agreement, the Company has agreed to indemnify and
hold him harmless to the fullest extent permitted by law, from any loss, damage
or liability incurred in the course of his employment.  The amount paid by the
Company is reducible by the amount of insurance paid to or on behalf of such
officer with respect to any event giving rise to indemnification.  Such
officer's right to indemnification is to survive his death or termination of
employment and the termination of his employment agreement.

ITEM 16. EXHIBITS AND FINANCIAL STATEMENT SCHEDULES

  (a)  Exhibits

<TABLE>
<C>            <S> 
     4         -   Specimen Common Stock Certificate (incorporated by reference to Exhibit 4
                   to the Company's Form S-1 Registration Statement (Reg. No. 33-33986)).
     5+        -   Opinion of Michael R. Patterson, Esq.
     23(a)+    -   Consent of Michael R. Patterson, Esq. (contained in Exhibit 5).
     23(b)+    -   Consent of Price Waterhouse LLP.
     23(c)+    -   Consent of Netherland, Sewell & Associates, Inc.
     23(d)+    -   Consent of H. J. Gruy and Associates, Inc.
     23(e)+    -   Consent of Ryder Scott Company.
     24+       -   Powers of Attorney (contained on page II-4 of this Registration Statement).
</TABLE>
----------
+ Filed herewith.

ITEM 17. UNDERTAKINGS

  (a)  The undersigned registrant hereby undertakes:

     (1) To file, during any period in which offers or sales are being made, a
post-effective amendment to this registration statement:  (i) to include any
prospectus required by Section 10(a)(3) of the Securities Act; (ii) to reflect
in the prospectus any facts or events arising after the effective date of the
registration statement (or the most recent post-effective amendment thereof)
which, individually or in the aggregate, represent a fundamental change in the
information set forth in the registration statement.  Notwithstanding the
foregoing, any increase or decrease in volume of securities offered (if the
total dollar value of securities offered would not exceed that which was
registered) and any deviation from the low or high end of the estimated maximum
offering range may be reflected in the form of prospectus filed with the
Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume
and price represent no more than 20% change in the maximum aggregate offering
price set forth in the "Calculation of Registration Fee" table in the effective
registration statement; (iii) to include any material information with respect
to the plan of distribution not previously disclosed in the registration
statement or any material change to such information in the registration
statement; provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not
apply if the information required to be included in a post-effective amendment
by those paragraphs is contained in periodic reports filed by the registrant
pursuant to Section 13 or Section 15(d) of the Exchange Act that are
incorporated by reference in the registration statement.

     (2) That, for the purpose of determining any liability under the Securities
Act, each such post-effective amendment shall be deemed to be a new registration
statement relating to the securities offered therein, and the offering of such
securities at that time shall be deemed to be the initial bona fide offering
thereof.

     (3) To remove from registration by means of a post-effective amendment any
of the securities being registered which remain unsold at the termination of the
offering.

                                      II-2
<PAGE>
 
  (b) The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

   (c) Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to directors, officers and controlling persons of the
registrant pursuant to the provisions described in Item 15 above, or otherwise,
the registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the registrant of expenses
incurred or paid by a director, officer or controlling person of the registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against policy
as expressed in the Securities Act and will be governed by the final
adjudication of such issue.

                                      II-3
<PAGE>
 
                               POWER OF ATTORNEY

  KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears below
constitutes and appoints Phillip D. Kramer and Michael R. Patterson, and each of
them, either one of whom may act without joinder of the other, his true and
lawful attorneys-in-fact and agents, with full power of substitution and
resubstitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all pre- and post- effective amendments to this
Registration Statement, and to file the same, with all exhibits thereto and
other documents in connection therewith, with the Securities and Exchange
Commission, granting unto said attorneys-in-fact and agents, and each of them,
full power and authority to do and perform each and every act and thing
requisite and necessary to be done in and about the premises, as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents, and each of them, or the
substitute or substitutes of any or all of them, may lawfully do or cause to be
done by virtue hereof.

                                   SIGNATURES

  Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing a Form S-3 and has duly caused Registration Statement to
be signed on its behalf by the undersigned, thereunto duly authorized, in the
City of Houston, State of Texas, on March 19, 1996.

                                       PLAINS RESOURCES INC.


                                       By: /s/ Greg L. Armstrong
                                          ------------------------ 
                                           Greg L. Armstrong
                                           President and Chief Executive Officer

  Pursuant to the requirements of the Securities Act of 1933, this Registration
Statement has been signed by the following persons, in the capacities indicated
on March 19, 1996.

             Signature                               Title
             ---------                               -----

         /s/ Greg L. Armstrong           President, Chief Executive Officer and 
         --------------------------      Director (Principal Executive Officer) 
             Greg L. Armstrong
                

         /s/ Cynthia A. Feeback          Controller (Principal Accounting 
         --------------------------                   Officer)  
             Cynthia A. Feeback


         /s/ Phillip D. Kramer           Vice President, Chief Financial 
         --------------------------          Officer and Treasurer 
             Phillip D. Kramer            (Principal Financial Officer) 


         /s/ Robert A. Bezuch                         Director 
         -------------------------- 
             Robert A. Bezuch      


         /s/ William M. Hitchcock                     Director 
         --------------------------- 
             William M. Hitchcock  

                                      II-4
<PAGE>
 
         /s/   Dan M. Krausse             Chairman of the Board and Director 
         --------------------------- 
               Dan M. Krausse
                                  
         /s/  John H. Lollar                          Director 
         ---------------------------- 
              John H. Lollar                    


         /s/  D. Irving Obrow                         Director 
         ---------------------------- 
              D. Irving Obrow     


         /s/  Robert V. Sinnott                       Director 
         ---------------------------- 
              Robert V. Sinnott      


         /s/   J. Taft Symonds                        Director 
         ---------------------------- 
               J. Taft Symonds      

                                      II-5
<PAGE>
 
                               INDEX TO EXHIBITS

<TABLE> 
<CAPTION> 
                                                                                                              SEQUENTIALLY
  EXHIBIT                                                                                                       NUMBERED
  NUMBER                                                                                                          PAGE
  -------                                                                                                         ----

<C>             <S>                                    
    4           -   Specimen Common Stock Certificate (incorporated by reference to Exhibit 4
                    to the Company's Form S-1 Registration Statement (Reg. No. 33-33986)).
    5+          -   Opinion of Michael R. Patterson, Esq.                                                           19
    23(a)+      -   Consent of Michael R. Patterson, Esq. (contained in Exhibit 5).                                
    23(b)+      -   Consent of Price Waterhouse LLP.                                                                20
    23(c)+      -   Consent of Netherland, Sewell & Associates, Inc.                                                21
    23(d)+      -   Consent of H. J. Gruy and Associates, Inc.                                                      22
    23(e)+      -   Consent of Ryder Scott Company.                                                                 23
    24+         -   Powers of Attorney (contained on page II-4 of this Registration Statement)                          
</TABLE> 
----------                                      
+  Filed herewith.