<PAGE>   1
                                                                    EXHIBIT 3(o)


              STATEMENT OF RESOLUTION ESTABLISHING SERIES OF SHARES

                                   designated

                            SERIES M PREFERENCE STOCK

                                       of

                          RELIANT ENERGY, INCORPORATED

                          Pursuant to Article 2.13D of
                       the Texas Business Corporation Act

                  Pursuant to the provisions of Article 2.13D of the Texas
Business Corporation Act, the undersigned corporation submits the following
statement for the purpose of establishing and designating a series of shares of
its Preference Stock, without par value, designated "Series M Preference Stock"
and fixing and determining the relative rights and preferences thereof:

                  1. The name of the corporation is RELIANT ENERGY, INCORPORATED
(the "Company").

                  2. The following resolution establishing and designating a
series of shares and fixing and determining the relative rights and preferences
thereof, was duly adopted by all necessary action on the part of the Company on
December 7, 2000:

                  RESOLVED, that pursuant to the authority vested in the Finance
         Committee and the Preference Stock Committee, acting separately and/or
         concurrently, by the Board of Directors of this Company in accordance
         with the provisions of the Restated Articles of Incorporation, a series
         of Preference Stock, without par value, of the Company be and hereby is
         created, and that the designation and number of shares thereof and the
         preferences, limitations and relative rights, including voting rights,
         of the shares of such series and the qualifications, limitations and
         restrictions thereof are as follows:

                            SERIES M PREFERENCE STOCK

                  1. Designation and Amount. There shall be a series of
Preference Stock that shall be designated as "Series M Preference Stock," and
the number of shares constituting such series shall be 1,575. Such number of
shares may be increased or decreased by resolution of the Finance Committee and
the Preference Stock Committee, acting separately and/or concurrently; provided,
however, that no decrease shall reduce the number of shares of Series M
Preference Stock to less than the number of shares then issued and outstanding
plus the number of shares issuable upon exercise of outstanding rights, options
or warrants or upon conversion of outstanding securities issued by the Company.


                                      -1-
<PAGE>   2


                  2. Certain Defined Terms.

                  Capitalized terms not otherwise defined herein shall have the
respective meanings ascribed to them in that certain Senior Credit Agreement
(the "Credit Agreement") to be entered into among Houston Industries FinanceCo,
LP, a Delaware limited partnership to be the Borrower thereunder, the Company,
the lenders parties thereto and Citibank, N.A., as the Administrative Agent, on
or after December 8, 2000. In addition, the following terms are used herein as
defined below:

                           (i) "Computed Dividend Portion" means, within any
         Dividend Interval Period, an amount equal to the interest expense
         accrued on the indebtedness for borrowed money of the Borrower from the
         prior Dividend Payment Date to the Determination Date for the current
         Dividend Interval Period.

                           (ii) "Determination Date" means the date occurring
         five Business Days prior to a Dividend Declaration Date.

                           (iii) "Dividend" means the dividend on the Series M
         Preference Stock declared by the Company's Board of Directors with
         respect to a Dividend Interval Period.

                           (iv) "Dividend Declaration Amount" means, as of any
         Determination Date, the Preliminary Dividend Amount, less the sum of
         (a) the Interest Reconciliation Amount, (b) the Support Agreement
         Reconciliation Amount, and (c) the Other Sources Reconciliation Amount.
         The Dividend Declaration Amount may be greater than or less than the
         Preliminary Dividend Amount.

                           (v) "Dividend Declaration Date" means the date on
         which Dividends on the Series M Preference Stock are declared (or would
         have been declared but for the fact that the amount of the Dividend
         determined in accordance herewith would have been zero) during a
         Dividend Interval Period by the Company's Board of Directors.

                           (vi) "Dividend Interval Period" means the period
         beginning on a Dividend Payment Date and extending to the next Dividend
         Payment Date.

                           (vii) "Dividend Payment Date" means the date
         occurring five Business Days after a Dividend Declaration Date.

                           (viii) "Interest Reconciliation Amount" means an
         amount equal to (a) the Preliminary Dividend Amount computed for the
         prior Dividend Interval Period, less (b) the actual interest expense
         accrued on the indebtedness for borrowed money of the Borrower during
         such period.

                           (ix) "Other Sources Reconciliation Amount" means the
         sum of (a) to the extent applied to pay interest on the indebtedness
         for borrowed money of the Borrower or available in cash on the current
         Determination Date therefor, the amount of income or cash proceeds
         received by the Borrower from sources other than pursuant to the
         Support Agreement (including, without limitation, interest received on
         loans to Affiliates), and (b) the cash proceeds of new borrowings under
         the Credit Agreement or any other Permitted


                                      -2-
<PAGE>   3


         Facility that are utilized to pay interest on outstanding borrowings
         thereunder, from the Determination Date occurring in the Prior Dividend
         Interval Period to the Determination Date occurring in the current
         Dividend Interval Period.

                           (x) "Preliminary Dividend Amount" means the sum of
         the Computed Dividend Portion and the Projected Dividend Portion.

                           (xi) "Projected Dividend Portion" means, within any
         Dividend Interval Period, an amount equal to the projected interest
         expense that will be accrued on the indebtedness for borrowed money of
         the Borrower from the Determination Date for such Dividend Interval
         Period to the Dividend Payment Date.

                           (xii) "Support Agreement Reconciliation Amount" means
         the amount of cash payments made pursuant to the Support Agreement by
         the Company to the Borrower from the Determination Date occurring in
         the immediately prior Dividend Interval Period to the Determination
         Date occurring in the current Dividend Interval Period.

                  3. Dividends and Distributions.

                  (A) Subject to the prior and superior rights of the holders of
(i) any shares of any series of Preference Stock ranking prior and superior to
the shares of Series M Preference Stock with respect to dividends and (ii) any
shares of Preferred Stock, the holders of shares of Series M Preference Stock,
in preference to the holders of shares of any class or series of stock of the
Company ranking junior to the Series M Preference Stock, shall be entitled to
receive the amounts set forth below, when, as and if declared by the Board of
Directors in the manner described below out of assets of the Company legally
available for the purpose:

                           (i) On every regularly scheduled meeting of the
         Company's Board of Directors while any shares of Series M Preference
         Stock remain outstanding, the Board of Directors shall declare an
         aggregate Dividend (if a positive amount) equal to the lesser of (a)
         the Dividend Declaration Amount or (b) the Excess Cash Flow projected
         to be available as of the applicable Dividend Payment Date with respect
         to the then current Dividend Interval Period.

                           (ii) If, with respect to any Dividend Interval
         Period, the aggregate Dividend declared by the Company's Board of
         Directors is less than the Dividend Declaration Amount for such
         Dividend Interval Period because the Excess Cash Flow projected to be
         available as of the applicable Dividend Payment Date is less than the
         Dividend Declaration Amount, the amount of such deficiency shall be
         added to the Dividend Declaration Amount computed for the next Dividend
         Interval Period and such aggregate amount shall become the Dividend
         Declaration Amount for such period. The Dividend for such succeeding
         Dividend Interval Period shall equal the Dividend Declaration Amount
         unless such amount would exceed the Excess Cash Flow projected to be
         available as of the applicable Dividend Payment Date, in which case the
         Dividend shall be the amount of the projected Excess Cash Flow.


                                      -3-
<PAGE>   4


                           (iii) The aggregate Dividends paid on the shares of
         Series M Preference Stock in accordance with this Section 3(A) shall be
         allocated pro rata on a share-by-share basis among all such shares at
         the time outstanding.

                  (B) Accrued but unpaid dividends shall not bear interest. The
Board of Directors may fix a record date for the determination of holders of
shares of Series M Preference Stock entitled to receive payment of a dividend or
distribution declared thereon.

                  4. Voting Rights. Except as otherwise required by law or the
Restated Articles of Incorporation of the Company or as otherwise provided
herein, the holders of shares of Series M Preference Stock shall have no voting
rights.

                  5. Certain Restrictions. At any time when dividends or
distributions payable on the Series M Preference Stock as provided in Section 3
are in arrears, thereafter and until all accrued and unpaid dividends and
distributions, whether or not declared, on shares of Series M Preference Stock
outstanding shall have been paid in full, the Company shall not:

                           (i) declare dividends on, or redeem or purchase or
         otherwise acquire for consideration any shares of stock ranking junior
         (either as to dividends or upon liquidation, dissolution or winding up)
         to the Series M Preference Stock; or

                           (ii) declare dividends on any shares of stock ranking
         on a parity (either as to dividends or upon liquidation, dissolution or
         winding up) with the Series M Preference Stock, except dividends
         declared ratably on the Series M Preference Stock and all such parity
         stock on which dividends are payable or in arrears in proportion to the
         total amounts to which the holders of all such shares are then
         entitled.

                  6. Reacquired Shares. Any shares of Series M Preference Stock
purchased or otherwise acquired by the Company in any manner whatsoever shall be
retired and canceled promptly after the acquisition thereof. All such shares
shall upon their cancellation become authorized but unissued shares of
Preference Stock and may be reissued as part of a new series of Preference Stock
to be created by resolution or resolutions of the Board of Directors, subject to
any conditions and restrictions on issuance set forth herein.

                  7. Liquidation, Dissolution or Winding Up.

                  (A) Upon any liquidation (voluntary or otherwise), dissolution
or winding up of the Company, no distribution shall be made to the holders of
shares of stock ranking junior (either as to dividends or upon liquidation,
dissolution or winding up) to the Series M Preference Stock unless, prior
thereto, the holders of shares of Series M Preference Stock shall have received
$100,000 per share, plus an amount equal to accrued and unpaid dividends and
distributions thereon, whether or not declared, to the date of such payment (the
"Series M Liquidation Preference"). Following the payment of the full amount of
the Series M Liquidation Preference, no additional distributions shall be made
to the holders of shares of Series M Preference Stock.

                  (B) In the event that there are not sufficient assets
available to permit payment in full of the Series M Liquidation Preference and
the liquidation preferences of all other series


                                      -4-
<PAGE>   5


of Preference Stock, if any, that rank on a parity with the Series M Preference
Stock, then such remaining assets shall be distributed ratably to the holders of
such parity shares in proportion to their respective liquidation preferences.

                  (C) Neither the merger or consolidation of the Company into or
with another corporation nor the merger or consolidation of any other
corporation into or with the Company shall be deemed to be a liquidation,
dissolution or winding up of the Company within the meaning of this Section 7,
but the sale, lease or conveyance of all or substantially all of the Company's
assets shall be deemed to be a liquidation, dissolution or winding up of the
Company within the meaning of this Section 7.

                  8. Redemption.

                  (A) The Company, at its option, may redeem shares of the
Series M Preference Stock in whole at any time and in part from time to time, at
a redemption price equal to $100,000 per share plus, in the event all
outstanding shares of the Series M Preference Stock are to be redeemed, unpaid
accumulated dividends to the date of redemption.

                  (B) In the event that fewer than all the outstanding shares of
the Series M Preference Stock are to be redeemed, the number of shares to be
redeemed shall be determined by the Board of Directors and the shares to be
redeemed shall be determined by lot or pro rata as may be determined by the
Board of Directors or by any other method that may be determined by the Board of
Directors in its sole discretion to be equitable.

                  (C) Except to the extent notice is waived in accordance with
applicable law, notice of any such redemption shall be given by mailing to the
holders of the shares of Series M Preference Stock to be redeemed a notice of
such redemption, first class postage prepaid, not later than the twentieth day
and not earlier than the sixtieth day before the date fixed for redemption, at
their last address as the same shall appear upon the books of the Company. Each
such notice shall state: (i) the redemption date; (ii) the number of shares to
be redeemed and, if fewer than all the shares held by such holder are to be
redeemed, the number of such shares to be redeemed from such holder; (iii) the
redemption price; (iv) the place or places where certificates for such shares
are to be surrendered for payment of the redemption price; and (v) that
dividends on the shares to be redeemed will cease to accrue on the close of
business on such redemption date. Any notice that is mailed in the manner herein
provided shall be conclusively presumed to have been duly given, whether or not
the shareholder received such notice, and failure duly to give such notice by
mail, or any defect in such notice, to any holder of Series M Preference Stock
shall not affect the validity of the proceedings for the redemption of any other
shares of Series M Preference Stock that are to be redeemed. On or after the
date fixed for redemption as stated in such notice, each holder of the shares
called for redemption shall surrender the certificate evidencing such shares to
the Company at the place designated in such notice and shall thereupon be
entitled to receive payment of the redemption price. If fewer than all the
shares represented by any such surrendered certificate are redeemed, a new
certificate shall be issued representing the unredeemed shares.

                  (D) The shares of Series M Preference Stock shall not be
subject to the operation of any purchase, retirement or sinking fund.


                                      -5-
<PAGE>   6


                  9. Ranking. The Series M Preference Stock shall rank junior to
all series of the Company's Preferred Stock and pari passu with all other series
of the Company's Preference Stock (other than any such series of Preference
Stock the terms of which shall provide otherwise) in respect to dividend and
liquidation rights and shall rank senior to the Common Stock as to such matters.

                  10. Amendment. At any time that any shares of Series M
Preference Stock are outstanding, the Restated Articles of Incorporation of the
Company shall not be amended in any manner which would materially alter or
change the powers, preferences or special rights of the Series M Preference
Stock so as to affect them adversely without the affirmative vote of the holders
of two-thirds or more of the outstanding shares of Series M Preference Stock,
voting separately as a class.

                  11. Fractional Shares. Series M Preference Stock may be issued
in fractions of a share that shall entitle the holder, in proportion to such
holder's fractional shares, to exercise any voting rights, receive dividends,
participate in distributions and to have the benefit of all other rights of
holders of Series M Preference Stock.


                 REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK


                                      -6-
<PAGE>   7


                  IN WITNESS WHEREOF, RELIANT ENERGY, INCORPORATED has caused
this Statement to be executed on its behalf by the undersigned officer this 20th
day of December, 2000.



                                            RELIANT ENERGY, INCORPORATED



                                            /s/ Marc Kilbride
                                            ----------------------------
                                            Name:  Marc Kilbride
                                            Title: Treasurer


                                      -7-