<PAGE>   1
                            
                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 10-Q


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

For the quarterly period ended September 30, 1998

                                       or

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


                         COMMISSION FILE NUMBER: 1-12473


                              ENRON CAPITAL TRUST I
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

 
           Delaware                                            76-0518948
(STATE OR OTHER JURISDICTION OF                             (I.R.S. EMPLOYER
 INCORPORATION OR ORGANIZATION)                             IDENTIFICATION NO.)



              Enron Bldg.
           1400 Smith Street
            Houston, Texas                                        77002
(ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)                        (ZIP CODE)


                                 (713) 853-6161
              (REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE)


      Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days.

                         [X] Yes          [ ] No

      As of September 30, 1998, the Registrant had an aggregate of 8,000,000 
8.30% Trust  Preferred  Securities and 247,440 8.30% Trust Common Securities 
outstanding.


                               Page 1 of 6 Pages

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                              ENRON CAPITAL TRUST I

                                    FORM 10-Q

                                      INDEX

                                                                        Page No.
PART I  -  FINANCIAL INFORMATION

ITEM 1.      Financial Statements (see Note below)                         3 

ITEM 2.      Management's Discussion and Analysis of Financial 
             Condition and Results of Operations (see Note below)          3


PART II  - OTHER INFORMATION

ITEM 1.      Legal Proceedings                                             4  

ITEM 2.      Changes in Securities                                         4

ITEM 3.      Defaults upon Senior Securities                               4

ITEM 4.      Submission of Matters to a Vote of Security Holders           4

ITEM 6.      Exhibits and Reports on Form 8-K                              4

SIGNATURES                                                                 5 
 

                                Page 2 of 6 Pages

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PART I   FINANCIAL INFORMATION

ITEM 1.  FINANCIAL STATEMENTS (SEE NOTE BELOW)

ITEM 2.  MANAGEMENT'S  DISCUSSION  AND ANALYSIS OF FINANCIAL  CONDITION
         AND RESULTS OF  OPERATIONS  (SEE NOTE BELOW)

         Enron Capital Trust I (the "Trust") is a statutory business trust
created under the Delaware Business Trust Act, as amended (the "Trust Act"),
pursuant to an amended and restated declaration of trust (the "Declaration") and
the filing of a certificate of trust with the Secretary of State of the State of
Delaware. The Trust's sole assets are 8,247,440 8.30% Partnership Preferred
Securities ($25 liquidation amount per security) representing an 85% limited
partnership interest in Enron Preferred Funding, L.P., a Delaware limited
partnership (the "Partnership"). Ownership of the assets of the Trust is
evidenced by an aggregate of 8,000,000 8.30% Trust Preferred Securities (the
"Trust Preferred Securities"), which are listed and traded on the New York Stock
Exchange under the symbol "ENE PrT", and 247,440 Trust Common Securities (the
"Trust Common Securities," and, together with the Trust Preferred Securities,
the "Trust Securities"), all of which are owned by Enron Corp., an Oregon
corporation ("Enron"). The Trust makes distributions on the Trust Securities to
the extent it receives distributions from the Partnership on the Partnership
Preferred Securities. Payments on the Partnership Preferred Securities represent
the sole source of revenue for the Trust. Distributions on the Trust Securities
are guaranteed by Enron, but only to the extent that the Trust has available
funds to pay such distributions. The Trust was created for the sole purpose of
issuing the Trust Securities, investing the proceeds of such issuance in the
Partnership Preferred Securities and engaging in only those other activities
necessary or incidental thereto. The Trust Securities are subject to redemption
at any time on or after March 31, 2002 and earlier in the event of certain tax
law changes or other events.

         The general partner of the Partnership is Enron, which owns a 15%
general partnership interest in the Partnership. Since completion of the
offering of the Trust Preferred Securities on November 21, 1996, the assets of
the Partnership have been invested primarily in a $181,926,000 principal amount
7.75% Subordinated Debenture due 2016 of Enron (the "Enron Debenture") and
$29,108,000 principal amount 7.75% Debentures due 2016 of each of Enron Capital
& Trade Resources Corp. and Enron Pipeline Company (the "Subsidiary Debentures"
and, together with the Enron Debenture, the "Debentures"), each of which is a
wholly owned subsidiary of Enron. The obligations under the Subsidiary
Debentures are guaranteed by Enron. The respective issuers of the Debentures
have certain rights to elect to defer any payments of principal and interest on
the Debentures for up to five years at a time. In addition to the Debentures,
the Partnership owns an aggregate of approximately $2,460,000 in short-term,
investment grade debt securities (the "Eligible Debt Securities"). Under certain
circumstances, upon repayment of one or more of the Debentures, the assets of
the Partnership may be reinvested in one or more debt securities of Enron or its
subsidiaries. Payments of interest and principal on the Enron Debenture and the
Subsidiary Debentures (or the guarantees thereof) and the Eligible Debt
Securities are the sole source of revenue for the Partnership. The Partnership
pays distributions to the Trust as holder of the Partnership Preferred
Securities when, as and if Enron, as the general partner, determines to do so,
although Enron has no obligation to do so.

      NOTE: Because the Trust and the Partnership are special purpose financing
entities with no separate business operations, the only assets of the Trust are
the Partnership Preferred Securities, and substantially all of the assets of the
Partnership consist of a debt security of Enron and debt securities of
subsidiaries of Enron that are guaranteed by Enron, the Trust does not believe
that financial statements for the Trust or the Partnership are meaningful.
Accordingly, financial statements and related financial information have not
been included in this Form 10-Q. For further information concerning Enron and
its subsidiaries, including financial statements and other financial
information, see the Enron Annual Report on Form 10-K for the year ended
December 31, 1997, and Enron Quarterly Report on Form 10-Q for the quarterly
period ended September 30, 1998, as filed with the Securities and Exchange
Commission, copies of which may be obtained from the Corporate Secretary of
Enron at the address listed on the cover of this Form 10-Q.


                               Page 3 of 6 Pages

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PART II      OTHER INFORMATION

ITEM 1.      LEGAL PROCEEDINGS

             None.

ITEM 2.      CHANGES IN SECURITIES

             None.

ITEM 3.      DEFAULTS UPON SENIOR SECURITIES

             None.

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

             None.

ITEM 6.      EXHIBITS AND REPORTS ON FORM 8-K

        (A)  EXHIBITS.

             4.1   Certificate of Trust  (incorporated  by reference to Exhibit 
                   4(a) of the  Registration  Statement on Form S-3 of the 
                   Trust  (No. 333-14967)).
             4.2   Amended and Restated Declaration of Trust dated as of 
                   November 18, 1996 (incorporated by reference to Exhibit 4.2
                   to Enron Capital Trust I Form 10-K for the year ended 
                   December 31, 1996 ("Form 10-K").
             4.3   Amended and Restated  Agreement of Limited  Partnership of 
                   Enron Preferred  Funding L.P. dated as of November 21, 1996 
                   (incorporated by reference to Exhibit 4.3 to Form 10-K).
             4.4   Trust Preferred  Guarantee  Agreement dated as of
                   November 21, 1996 (incorporated by reference to Exhibit 4.4 
                   to Form 10-K).
             4.5   Partnership  Preferred  Guarantee  Agreement  dated as of 
                   November  21,  1996  (incorporated  by reference to Exhibit 
                   4.5 to Form 10-K).
             4.6   Indenture dated as of November 21, 1996 relating to the
                   Enron's 7.75% Subordinated Debentures due 2016 (incorporated
                   by reference to Exhibit 4.6 to Form 10-K).
             4.7   Indenture dated as of November 21, 1996 relating to Enron
                   Pipeline Company's 7.75% Debentures due 2016 (incorporated by
                   reference to Exhibit 4.7 to Form 10-K).
             4.8   Indenture dated as of November 21, 1996 relating to the Enron
                   Capital & Trade Resources Corp. 7.75% Debentures due 2016
                   (incorporated by reference to Exhibit 4.8 to Form 10-K).
             4.9   Guarantee Agreement of Enron dated as of November 21, 1996
                   relating to Enron Pipeline Company's 7.75% Debentures due 
                   2016 (incorporated by reference to Exhibit 4.9 to Form 10-K).
             4.10  Guarantee Agreement of Enron dated as of November 21, 1996
                   relating to Enron Capital & Trade Resources Corp. 7.75%
                   Debentures due 2016 (incorporated by reference to Exhibit
                   4.10 to Form 10-K).
             4.11  Form of certificate representing Trust Preferred Securities 
                   (included in Exhibit 4.2).
             27.1  Financial Data Schedule.

        (B)  REPORTS ON FORM 8-K.

             None.


                               Page 4 of 6 Pages

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                                   SIGNATURES

      Pursuant to the requirements 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.

                                                  ENRON CAPITAL TRUST I
                                                      (Registrant)
            


Date: September 13, 1998                          By: /s/  KEITH A. CRANE     
                                                     ---------------------------
                                                     Name:  Keith A. Crane
                                                     Title: Regular Trustee


                                                      /s/  PHILLIP M. SISNEROS
                                                     ---------------------------
                                                     Name:  Phillip M. Sisneros
                                                     Title: Regular Trustee


                               Page 5 of 6 Pages

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                                INDEX TO EXHIBITS

EXHIBIT
  NO.                               DESCRIPTION

 4.1     Certificate of Trust  (incorporated  by reference to Exhibit 4(a) of
         the Registration  Statement on Form S-3 of the Trust (No. 333-14967)).
 4.2     Amended and Restated Declaration of Trust dated as of November
         18, 1996 (incorporated by reference to Exhibit 4.2 to Enron
         Capital Trust I Form 10-K for the year ended December 31, 1996
         ("Form 10-K").
 4.3     Amended and Restated  Agreement of Limited  Partnership of Enron 
         Preferred  Funding L.P. dated a of November 21, 1996 (incorporated by 
         reference to Exhibit 4.3 to Form 10-K).
 4.4     Trust Preferred  Guarantee  Agreement dated as of November 21, 1996 
         (incorporated by reference to Exhibit 4.4 to Form 10-K).
 4.5     Partnership Preferred Guarantee Agreement dated as of November 21, 
         1996 (incorporated  by reference to Exhibit 4.5 to Form 10-K).
 4.6     Indenture dated as of November 21, 1996 relating to the Enron's 7.75%
         Subordinated Debentures due 2016 (incorporated by reference to Exhibit 
         4.6 to Form 10-K).
 4.7     Indenture dated as of November 21, 1996 relating to Enron Pipeline 
         Company's 7.75% Debentures due 2016 (incorporated by reference to
         Exhibit 4.7 to Form 10-K).
 4.8     Indenture dated as of November 21, 1996 relating to the Enron
         Capital & Trade Resources Corp. 7.75% Debentures due 2016
         (incorporated by reference to Exhibit 4.8 to Form 10-K).
 4.9     Guarantee Agreement of Enron dated as of November 21, 1996 relating to 
         Enron Pipeline Company's 7.75% Debentures due 2016 (incorporated by 
         reference to Exhibit 4.9 to Form 10-K).
 4.10    Guarantee Agreement of Enron dated as of November 21, 1996 relating to
         Enron Capital & Trade Resources Corp. 7.75% Debentures due 2016
         (incorporated by reference to Exhibit 4.10 to Form 10-K).
 4.11    Form of certificate representing Trust Preferred Securities (included 
         in Exhibit 4.2).
 27.1    Financial Data Schedule.


                               Page 6 of 6 Pages