EXHIBIT 4.2
 
No. SB 0001                                                       $25,786,500.00
CUSIP No. 844 767 AA1

                            SOUTHWEST BANCORP, INC.
                         9.30% SUBORDINATED DEBENTURE
                               DUE JULY 31, 2027

     Southwest Bancorp, Inc., an Oklahoma corporation (the "Company," which term
includes any successor corporation under the Indenture hereinafter referred to),
for value received, hereby promises to pay to, State Street Bank and Trust
Company as Property Trustee for SBI Capital Trust or registered assigns, the
principal sum of Twenty Five Million Seven Hundred Eighty Six Thousand Five
Hundred Dollars and no cents ($25,786,500.00) on July 31, 2027 (the "Stated
Maturity"), and to pay interest on said principal sum from June 4, 1997, or from
the most recent interest payment date (each such date, an "Interest Payment
Date") to which interest has been paid or duly provided for, quarterly (subject
to deferral as set forth herein) in arrears on January 31, April 30, July 31 and
October 31 of each year commencing July 31, 1997, at the rate of 9.30% per annum
until the principal hereof shall have become due and payable, and on any overdue
principal and (without duplication) on any overdue installment of interest at
the same rate per annum compounded quarterly. The amount of interest payable on
any Interest Payment Date shall be computed on the basis of a 360-day year of
twelve 30-day months.  The amount of interest for any partial period shall be
computed on the basis of the number of days elapsed in a 360-day year of twelve
30-day months.  In the event that any date on which interest is payable on this
Debenture is not a business day, then payment of interest payable on such date
shall be made on the next succeeding day that is a business day (and without any
interest or other payment in respect of any such delay) with the same force and
effect as if made on such date. The interest installment so payable, and
punctually paid or duly provided for, on any Interest Payment Date shall, as
provided in the Indenture, be paid to the person in whose name this Debenture
(or one or more Predecessor Debentures, as defined in said Indenture) is
registered at the close of business on the regular record date for such interest
installment, which shall be the close of business on the fifteenth day of the
month in which the Interest Payment Date occurs, unless otherwise provided in
the Indenture. Any such interest installment not punctually paid or duly
provided for shall forthwith cease to be payable to the registered holders on
such regular record date and may be paid to the Person in whose name this
Debenture (or one or more Predecessor Debentures) is registered at the close of
business on a special record date to be fixed by the Trustee for the payment of
such defaulted interest, notice whereof shall be given to the registered holders
of the Debentures not less than 10 days prior to such special record date, or
may be paid at any time in any other lawful manner not inconsistent with the
requirements of any securities exchange on which the Debentures may be listed,
and upon such notice as may be required by such exchange, all as more fully
provided in the Indenture. The principal of and the interest on this Debenture
shall be payable at the office or agency of the Trustee maintained for that
purpose in any coin or currency of the United States of America that at the time
of payment is legal tender for payment of public and private debts; provided,
however, that payment of interest may be made at the option of the Company by
check mailed to the registered holder at such address as shall appear in the
Debenture Register. Notwithstanding the foregoing, so long as the holder of this
Debenture is the Property Trustee, the payment of the principal of and interest
on this Debenture shall be made at such place and to such account as may be
designated by the Trustee.

     The Stated Maturity may be shortened at any time by the Company to any date
not earlier than July 31, 2002, subject to the Company having received prior
approval of the Federal Reserve, if then required under applicable capital
guidelines or policies of the Federal Reserve. Such date may also be extended at
any time at the election of the Company for one or more periods, but in no event
to a date later than July 31, 2036, subject to certain limitations described in
the Indenture.

     The indebtedness evidenced by this Debenture is, to the extent provided in
the Indenture, subordinate and junior in right of payment to the prior payment
in full of all Senior Indebtedness, and this Debenture is issued subject to the
provisions of the Indenture with respect thereto. Each holder of this Debenture,
by accepting the same, (a) agrees to and shall be bound by such provisions; (b)
authorizes and directs the Trustee on his or her behalf to take such action as
may be necessary or appropriate to acknowledge or effectuate the subordination
so provided; and (c) appoints the Trustee his or her attorney-in-fact for any
and all such purposes. Each holder hereof, by his or her acceptance hereof,
hereby waives all notice of the acceptance of the subordination provisions
contained herein and in the Indenture by each holder of Senior Indebtedness,
whether now outstanding or hereafter incurred, and waives reliance by each such
holder upon said provisions.

     This Debenture shall not be entitled to any benefit under the Indenture
hereinafter referred to, be valid or become obligatory for any purpose until the
Certificate of Authentication hereon shall have been signed by or on behalf of
the Trustee.

     The provisions of this Debenture are continued on the reverse side hereof
and such continued provisions shall for all purposes have the same effect as
though fully set forth at this place.

     IN WITNESS WHEREOF, the Company has caused this instrument to be executed.

Dated: June 4, 1997

Attest: -SPECIMEN-                         SOUTHWEST BANCORP, INC.

By: ______________-SPECIMEN-_____    By:_-SPECIMEN____________________________
    Deborah T. Bradley, Secretary            Robert L. McCormick, Jr., President

                         CERTIFICATE OF AUTHENTICATION

  This is one of the Debentures described in the within-mentioned Indenture.

Dated: June 4, 1997

STATE STREET BANK AND TRUST COMPANY,
as Trustee

By ______________________________        
   Paul D. Allen, Vice President

 
                         9.30% SUBORDINATED DEBENTURE
                                  (CONTINUED)

     This Debenture is one of the subordinated debentures of the Company (herein
sometimes referred to as the "Debentures"), specified in the Indenture, all
issued or to be issued under and pursuant to an Indenture dated as of June 4,
1997 (the "Indenture") duly executed and delivered between the Company and State
Street Bank and Trust Company, as Trustee (the "Trustee"), to which Indenture
reference is hereby made for a description of the rights, limitations of rights,
obligations, duties and immunities thereunder of the Trustee, the Company and
the holders of the Debentures. The Debentures are limited in aggregate principal
amount as specified in the Indenture.

     In certain circumstances, because of the occurrence and continuation of a
Special Event, this Debenture may become due and payable prior to its Stated
Maturity, at the principal amount together with any interest accrued thereon
(the "Redemption Price"). The Redemption Price shall be paid prior to 12:00
noon, Eastern Time, on the date of such redemption or at such earlier time as
the Company determines. The Company shall have the right to redeem this
Debenture at the option of the Company, without premium or penalty, in whole or
in part at any time on or after July 31, 2002 (an "Optional Redemption"), or at
any time in certain circumstances upon the occurrence of a Special Event, at a
Redemption Price equal to 100% of the principal amount plus any accrued but
unpaid interest, to the date of such redemption. Any redemption pursuant to this
paragraph shall be made upon not less than 30 days nor more than 60 days notice,
at the Redemption Price. If the Debentures are only partially redeemed by the
Company pursuant to an Optional Redemption, the Debentures shall be redeemed pro
rata or by lot or by any other method utilized by the Trustee.

     In the event of redemption of this Debenture in part only, a new Debenture
or Debentures for the unredeemed portion hereof shall be issued in the name of
the holder hereof, upon the cancellation hereof.

     In case an Event of Default, as defined in the Indenture, shall have
occurred and be continuing, the principal of all of the Debentures may be
declared, and upon such declaration shall become, due and payable, in the
manner, with the effect and subject to the conditions provided in the Indenture.

     The Indenture contains provisions permitting the Company and the Trustee,
with the consent of the holders of not less than a majority in aggregate
principal amount of the Debentures at the time outstanding, as defined in the
Indenture, to execute supplemental indentures for the purpose of adding any
provisions to or changing in any manner or eliminating any of the provisions of
the Indenture or of any supplemental indenture or of modifying in any manner the
rights of the holders of the Debentures; provided, however, that no such
supplemental indenture shall (i) extend the fixed maturity of the Debentures
except as provided in the Indenture, or reduce the principal amount thereof, or
reduce the rate or extend the time of payment of interest thereon, without the
consent of the holder of each Debenture so affected; or (ii) reduce the
aforesaid percentage of Debentures, the holders of which are required to consent
to any such supplemental indenture, without the consent of the holders of each
Debenture then outstanding and affected thereby. The Indenture also contains
provisions permitting the holders of a majority in aggregate principal amount of
the Debentures at the time outstanding, on behalf of all of the holders of the
Debentures, to waive any past default in the performance of any of the covenants
contained in the Indenture, or established pursuant to the Indenture, and its
consequences, except a default in the payment of the principal of or interest on
any of the Debentures. Any such consent or waiver by the registered holder of
this Debenture (unless revoked as provided in the Indenture) shall be conclusive
and binding upon such holder and upon all future holders and owners of this
Debenture and of any Debenture issued in exchange herefor or in place hereof
(whether by registration of transfer or in place hereof, irrespective of whether
or not any notation of such consent or waiver is made upon this Debenture).

     No reference herein to the Indenture and no provision of this Debenture or
of the Indenture shall alter or impair the obligation of the Company, which is
absolute and unconditional, to pay the principal and interest on this Debenture
at the time and place and at the rate and in the money herein prescribed.

     The Company shall have the right at any time during the term of the
Debentures and from time to time to extend the interest payment period of such
Debentures for up to 20 consecutive quarters (each, an "Extended Interest
Payment Period"), at the end of which period the Company shall pay all interest
then accrued and unpaid (together with interest thereon at the rate specified
for the Debentures to the extent that payment of such interest is enforceable
under applicable law). Before the termination of any such Extended Interest
Payment Period, the Company may further extend such Extended Interest Payment
Period, provided that such Extended Interest Payment Period, together with all
such further extensions thereof, shall not exceed 20 consecutive quarters. At
the termination of any such Extended Interest Payment Period and upon the
payment of all accrued and unpaid interest and any additional amounts then due,
the Company may commence a new Extended Interest Payment Period.

     As provided in the Indenture and subject to certain limitations therein set
forth, this Debenture is transferable by the registered holder hereof on the
Debenture Register of the Company, upon surrender of this Debenture for
registration of transfer at the office or agency of the Trustee accompanied by a
written instrument or instruments of transfer in form satisfactory to the
Company or the Trustee duly executed by the registered holder hereof or his
attorney duly authorized in writing, and thereupon one or more new Debentures of
authorized denominations and for the same aggregate principal amount shall be
issued to the designated transferee or transferees. No service charge shall be
made for any such transfer, but the Company may require payment of a sum
sufficient to cover any tax or other governmental charge payable in relation
thereto.

     Prior to due presentment for registration of transfer of this Debenture,
the Company, the Trustee, any paying agent and the Debenture Registrar may deem
and treat the registered holder hereof as the absolute owner hereof (whether or
not this Debenture shall be overdue and notwithstanding any notice of ownership
or writing hereon made by anyone other than the Debenture Registrar) for the
purpose of receiving payment of or on account of the principal hereof and
interest due hereon and for all other purposes, and neither the Company nor the
Trustee, nor any paying agent, nor any Debenture Registrar shall be affected by
any notice to the contrary.

     No recourse shall be had for the payment of the principal of or the
interest on this Debenture, or for any claim based hereon, or otherwise in
respect hereof, or based on or in respect of the Indenture, against any
incorporator, stockholder, officer or director, past, present or future, as
such, of the Company or of any predecessor or successor corporation, whether by
virtue of any constitution, statute or rule of law, or by the enforcement of any
assessment or penalty or otherwise, all such liability being, by the acceptance
hereof and as part of the consideration for the issuance hereof, expressly
waived and released.

     The Debentures are issuable only in registered form without coupons in
denominations of $25 and any integral multiple thereof.

     All terms used in this Debenture that are defined in the Indenture shall
have the meanings assigned to them in the Indenture.