<Page>

THIS SECURITY IS A GLOBAL SECURITY AS REFERRED TO IN THE INDENTURE HEREINAFTER
REFERENCED. UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR THE
INDIVIDUAL SECURITIES REPRESENTED HEREBY, THIS GLOBAL SECURITY MAY NOT BE
TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY
OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE
DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR
A NOMINEE OF SUCH SUCCESSOR DEPOSITARY.

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK) TO THE ISSUER OR
ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS REQUESTED
BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY AND ANY PAYMENT
IS MADE TO CEDE & CO., ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE REGISTERED OWNER HEREOF,
CEDE & CO., HAS AN INTEREST HEREIN.


                              QUESTAR GAS COMPANY
                           MEDIUM-TERM NOTE, SERIES D
                                  (FIXED RATE)

<Table>
<Caption>

REGISTERED                                                     PRINCIPAL AMOUNT
NO. FXR-__                                                         $___________

<S>                                 <C>
CUSIP No.:_________


Original Issue Date:____             Interest Rate:__%

Stated Maturity:____                 Sinking Fund/Repayment Provision:__

Interest Payment Date(s):            Optional Repayment Date:__
April 1 and October 1

Regular Record Date(s):              Optional Redemption: see below
March 15 and September 15

Authorized Determination:            Redemption Percentage: see below

Specified Currency:                  Annual Redemption Percentage: see below

Exchange Rate Agent:                 Redemption Commencement Date: see below

Default Rate:                        Redemption Date: see below

Other Provisions: Terms are not      Redemption Price: see below
completed for certain items above
either because such items are not
applicable or because the terms are
as specified in the Prospectus.

</Table>


<Page>

         QUESTAR GAS COMPANY, a corporation duly organized and existing under
the laws of the State of Utah (herein called the "Company", which term includes
any successor corporation under the Indenture hereinafter referred to), for
value received, hereby promises to pay to CEDE & CO., or registered assigns, the
principal sum of _____________________________________________________ DOLLARS
($______________) at Stated Maturity as specified above (except to the extent
redeemed or repaid prior to the Stated Maturity), and to pay interest thereon
from the Original Issue Date specified above or from the most recent Interest
Payment Date (subject to the provisions below) to which interest has been paid
or duly provided for, periodically on each Interest Payment Date, commencing
with the first such Interest Payment Date next succeeding the Original Issue
Date specified above, and at Stated Maturity (the date on each such Stated
Maturity, Redemption Date, and Optional Repayment Date and the date on which
principal or an installment of principal is due and payable by declaration of
acceleration pursuant to the Indenture being referred to hereinafter as a
"Maturity" with respect to principal payable on such date), at the Interest Rate
specified above, until the principal hereof is paid or made available for
payment; PROVIDED, that if such Original Issue Date is after a Regular Record
Date and before the Interest Payment Date immediately following such Regular
Record Date, interest payments will commence on the second Interest Payment Date
following the Original Issue Date. The interest so payable, and punctually paid
or duly provided for, on any Interest Payment Date (except at Maturity) will, as
provided in the Indenture, be paid to the Person in whose name this Note (or one
or more Notes which are Predecessor Securities) is registered at the close of
business on the Regular Record Date next preceding such Interest Payment Date.
Any such interest which is payable, but not so punctually paid or duly provided
for on any Interest Payment Date, will forthwith cease to be payable to the
Holder on such Regular Record Date and may either be paid to the Person in whose
name this Note (or one or more Notes which are Predecessor Securities) is
registered at the close of business on a Special Record Date for the payment of
such Defaulted Interest to be fixed by the Trustee, notice whereof shall be
given to the Holder of this Note not less than 10 days prior to such Special
Record Date, or be paid at any time in any other lawful manner not inconsistent
with the requirements of any securities exchange on which the Notes of this
series may be listed, upon such notice as may be required by such exchange, all
as more fully provided in the Indenture. Reference herein to "this Note",
"hereof", "herein" and comparable terms shall include an Addendum hereto if an
Addendum is specified above.

                  Any provision contained herein with respect to the calculation
of the rate of interest applicable to this Note, its payment dates or any other
matter relating


                                       2
<Page>

hereto may be modified as specified in an Addendum relating hereto if so
specified above.

                  This Note is one of a duly authorized series of debt
securities of the Company (herein called the "Securities"), and the series
thereof to which this Note belongs, being issued and to be issued under an
Indenture, dated as of May 1, 1992 (herein called the "Indenture"), between the
Company and Wells Fargo Bank Northwest, National Association (f/k/a First
Security Bank, N.A.), as successor trustee to Citibank, N.A. (herein called the
"Trustee", which term includes any successor trustee under the Indenture), and
reference is hereby made to the Indenture and all indentures supplemental
thereto for a statement of the respective rights, limitations of rights, duties
and immunities thereunder of the Company, the Trustee and the Holders of the
Notes and of the terms upon which the Notes are, and are to be, authenticated
and delivered. This Note is one of the series of Securities designated as
"Medium-Term Notes, Series D." The Notes may be issued from time to time at
varying maturities, interest rates and other terms and in an aggregate principal
amount up to $100,000,000, which amount may be increased if duly authorized by
the Company.

                  Unless otherwise specified on the first page hereof, the
Interest Payment Dates with respect to this Note will be April 1 and October
1 of each year, and the Regular Record Dates in respect of such Interest
Payment Dates will be the immediately preceding March 15 and September 15
(whether or not a Business Day), respectively. If any Interest Payment Date or
Maturity with respect to this Note falls on a day that is not a Business Day,
the payment due on such Interest Payment Date or at Maturity will be made on the
following day that is a Business Day with respect to this Note as if it were
made on the date such payment was due and no interest shall accrue on the amount
so payable for the period from and after such Interest Payment Date or Maturity,
as the case may be. Unless otherwise specified on the first page of this Note,
the Interest Rate on this Note will be computed on the basis of a 360-day year
of twelve 30-day months. "Business Day" means any day that is not a Saturday or
Sunday and that in the Place of Payment is not a day on which banking
institutions are authorized or obligated by law or executive order to close.

                  If this Note is a definitive Note, payments of the principal,
premium, if any, and interest payable at Maturity on this Note will be made in
immediately available funds at the Corporate Trust Office of the Trustee in Salt
Lake City, Utah, or at such other place as the Company may designate, provided
that this Note is presented to the Trustee in time for the Trustee to make such
payments in such funds in


                                       3
<Page>

accordance with its normal procedures. Interest (other than interest payable
at Maturity) will be paid by check mailed to the address of the Person
entitled thereto as it appears in the Security Register as of the Regular
Record Date or, at the option of the Company, by wire transfer to an account
maintained by such Person with a bank located within the United States;
PROVIDED, HOWEVER, that if the Holder of this Note holds $10,000,000 or more
in the aggregate principal amount, such Holder may be entitled to receive
payments of principal, premium, if any, and interest by wire transfer to an
account maintained by such Holder with a bank located in the United States if
an appropriate written request has been received by the Trustee prior to the
Regular Record Date in respect of any interest payment, or the date which is
fifteen days before the Stated Maturity of the Note, as the case may be.

                  If this Note is a Global Security representing Book-Entry
Securities, payments of the principal of, premium, if any, and interest on the
Note will be made by check or by wire transfer to an account maintained by the
Depositary for such purpose.

                  This Note will be redeemable as a whole or in part, at the
option of the Company at any time, at a Redemption Price equal to the greater of
(i) 100% of its principal amount and (ii) the sum of the present values of the
remaining scheduled payments of principal and interest thereon discounted to the
Redemption Date on a semiannual basis (assuming a 360-day year consisting of
twelve 30-day months) at the Treasury Rate plus [ ] basis points, plus in each
case accrued and unpaid interest thereon to the date of redemption.

                  "Treasury Rate" means, with respect to any Redemption Date,
the rate per annum equal to the semiannual equivalent yield to maturity or
interpolated (on a day count basis) of the Comparable Treasury Issue, assuming a
price for the Comparable Treasury Issue (expressed as a percentage of its
principal amount) equal to the Comparable Treasury Price for such Redemption
Date.

                  "Comparable Treasury Issue" means the United States Treasury
security or securities selected by an Independent Investment Banker as having a
maturity or interpolated (on a day count basis) comparable to the remaining term
of this Note that would be utilized, at the time of selection and in accordance
with customary financial practice, in pricing new issues of corporate debt
securities of a comparable maturity to the remaining term of this Note.
"Independent Investment Banker" means one of the Reference Treasury Dealers
appointed by the Trustee after consultation with the Company.


                                       4
<Page>

                  "Comparable Treasury Price" means, with respect to any
Redemption Date, (i) the average of the Reference Treasury Dealer Quotations for
such Redemption Date, after excluding the highest and lowest such Reference
Treasury Dealer Quotations, or (ii) if the Trustee obtains fewer than four such
Reference Treasury Dealer Quotations, the average of all such quotations.
"Reference Treasury Dealer Quotations" means, with respect to each Reference
Treasury Dealer and any redemption date, the average, as determined by the
Trustee, of the bid and asked prices for the Comparable Treasury Issue
(expressed in each case as a percentage of its principal amount) quoted in
writing to the Trustee by such Reference Treasury Dealer at 3:30 p.m. New York
time on the third business day preceding such Redemption Date.

                  "Reference Treasury Dealer" means each of Merrill Lynch,
Pierce, Fenner & Smith Incorporated, Banc One Capital Markets, Inc. and U.S.
Bancorp Piper Jaffray Inc. and their respective successors; provided, however,
that if any of the foregoing or their affiliates shall cease to be a primary
U.S. Government securities dealer in The City of New York (a "Primary Treasury
Dealer"), the Company shall substitute therefor another Primary Treasury Dealer.

                  Notice of any redemption will be mailed at least 30 days but
not more than 60 days before the Redemption Date to the Holder of this Note.

                  Unless the Company defaults in payment of the Redemption
Price, on and after the Redemption Date interest will cease to accrue on this
Note or portions thereof called for redemption.

                  In the event of redemption of this Note in part only, a new
Note for the unredeemed portion hereof will be issued in the name of the Holder
hereof upon the cancellation hereof.

                  If so provided on the first page of this Note, this Note will
be subject to repayment at the option of the Holder hereof on the Optional
Repayment Date, if any, indicated on the first page hereof. If no Optional
Repayment Date is set forth on the first page hereof, this Note will not be
repayable at the option of the Holder prior to Stated Maturity. On any Optional
Repayment Date, this Note will be repayable in whole or in part in increments of
$1,000 at the option of the Holder hereof at a price equal to 100% of the
principal amount to be repaid, together with interest thereon payable to the
Optional Repayment Date, on notice in the form entitled "Option to Elect
Repayment" below, duly completed, given together with this Note by such Holder
to the Company not more than 60 nor less than 30 days prior to the Optional
Repayment Date. In the event of repayment of this Note in part only, a new Note
for


                                       5
<Page>

the portion hereof not repaid will be issued in the name of the Holder
hereof upon the surrender hereof. Exercise of such repayment option by the
Holder shall be irrevocable.

                  If an Event of Default with respect to the Notes shall occur
and be continuing, the principal of all of the Notes may be declared due and
payable in the manner and with the effect provided in the Indenture.

                  The Notes are subject to satisfaction, discharge and
defeasance as provided in Section 403 of the Indenture.

                  The Indenture permits, with certain exceptions as therein
provided, the amendment thereof and the modification of the rights and
obligations of the Company and the rights of the Holders of the Securities of
each series to be affected under the Indenture at any time by the Company and
the Trustee with the consent of the Holders of a majority in principal amount of
the Securities at the time Outstanding or, in the case less than all of the
several series of Securities are affected, the holders of a majority in
aggregate principal amount of the Securities at the time Outstanding of each
series to be affected. The Indenture also contains provisions permitting the
Holders of specified percentages in aggregate principal amount of the Securities
of each series at the time Outstanding, on behalf of the Holders of all
Securities of such series, to waive compliance by the Company with certain
provisions of the Indenture and certain past defaults under the Indenture and
their consequences. Any such consent or waiver by the Holder of this Note shall
be conclusive and binding upon such Holder and upon such future Holders of this
Note and of any Note issued upon the registration or transfer hereof or in
exchange herefor or in lieu hereof, whether or not notation of such consent or
waiver is made upon this Note.

                  No reference herein to the Indenture and no provision of this
Note or of the Indenture shall alter or impair the obligation of the Company,
which is absolute and unconditional, to pay the principal of, premium, if any,
and interest on this Note at the times, place and rate, and in the coin or
currency, herein prescribed.

                  As provided in the Indenture and subject to certain
limitations therein set forth, the transfer of this Note is registrable in the
Security Register, upon surrender of this Note for registration of transfer at
the office or agency of the Company in Salt Lake City, Utah, or at such other
place as the Company may designate from time to time, duly endorsed by, or
accompanied by a written instrument of transfer in form satisfactory to the
Company and the Security Register duly


                                       6
<Page>

executed by, the Holder hereof or his attorney duly authorized in writing,
and thereupon one or more new Notes, of authorized denominations and for the
same aggregate principal amount, will be issued to the designated transferee
or transferees.

                  The Notes are issuable in registered form without coupons in
minimum denominations of $1,000 or any amount in excess thereof that is an
integral multiple of $1,000. As provided in the Indenture and subject to certain
limitations therein set forth, Notes are exchangeable for a like aggregate
principal amount of Notes of different authorized denominations, as requested by
the Holder surrendering the same.

                  No service charge shall be made for any such registration of
transfer or exchange, but the Company may require payment of a sum sufficient to
cover any tax or other governmental charge payable in connection therewith.

                  Prior to due presentment of this Note for registration of
transfer, the Company, the Trustee and any agent of the Company or the Trustee
may treat the Person in whose name this Note is registered as the owner hereof
for all purposes, whether or not this Note be overdue, and neither the Company,
the Trustee nor any such agent shall be affected by notice to the contrary.

                  All terms used in this Note which are defined in the Indenture
shall have the meaning assigned to them in the Indenture.

                  THE INDENTURE AND THE NOTES, INCLUDING THIS NOTE, SHALL BE
GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK
APPLICABLE TO AGREEMENTS MADE AND TO BE PERFORMED IN SUCH STATE.

                  Unless the certificate of authentication hereon has been
executed by Wells Fargo Bank Northwest, National Association (f/k/a/ First
Security Bank, N.A.), the Trustee under the Indenture, or its successor
thereunder, by the manual signature of one of its authorized officers, this Note
shall not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.


                                       7
<Page>

                  IN WITNESS WHEREOF, the Company has caused this instrument to
be duly executed, manually or in facsimile, and a facsimile of its corporate
seal to be imprinted hereon.

                               QUESTAR GAS COMPANY



                               By:_________________________
                                  Name:
                                  Title:


ATTEST:

By:_____________________
   Name:
   Title:



[SEAL]


Date:


TRUSTEE'S CERTIFICATE OF AUTHENTICATION:
This is one of the Securities of the
series designated herein, referred to in
the within-mentioned Indenture.

Wells Fargo Bank Northwest, National Association (f/k/a First Security Bank,
N.A.), as Trustee


By:______________________________
   Authorized Signatory


                                       8
<Page>

                           ------------------------

                  The following abbreviations when used in the inscription on
this Note, shall be construed as though they were written out in full according
to applicable laws or regulations:


TEN COM - as tenants in common  UNIF GIFT MIN ACT - ______ Custodian_________
TEN ENT - as tenants by the                         (Cust)           (Minor)
               entireties                           Under Uniform Gifts to Minor
JT TEN - as joint tenants with                      Act_________________________
               right of survivorship                           (State)
               and not as tenants
               in common

   Additional abbreviations may also be used though not in the above list.

                           ------------------------

                  FOR VALUE RECEIVED, the undersigned hereby sells, assigns and
transfers unto


PLEASE INSERT SOCIAL SECURITY OR OTHER
IDENTIFYING NUMBER OF ASSIGNEE

--------------------------------------

--------------------------------------


--------------------------------------------------------------------------------
(Please print or typewrite name and address including postal zip code of
assignee)


--------------------------------------------------------------------------------
the within Note of Questar Gas Company and does hereby irrevocably constitute
and appoint


___________________________________________________________________ Attorney to
transfer said Note on the books of said Company, with full power of substitution
in the premises.

Dated:

         NOTICE: The signature of the Holder to this assignment must correspond
with the name as it appears upon the face of the within Note in every
particular, without alteration or enlargement or any change whatsoever, and be
guaranteed by an acceptable bank or broker.

<Page>

                            OPTION TO ELECT REPAYMENT

               The undersigned hereby irrevocably requests and instructs the
Company to repay the within Note (or portion hereof specified below) pursuant to
its terms at a price equal to 100% of the principal amount hereof, together with
interest thereon payable to the Optional Repayment Date, to the undersigned at

________________________________

_______________________________________________________________________________
(Please Print or Typewrite Name and Address of the Undersigned)

               For this Note to be repaid, the trustee must receive this "Option
to Elect Repayment" form, duly completed, together with this Note not more than
60 nor less than 30 days prior to an Optional Repayment Date shown on the face
of this Note at its Corporate Trust Office, or at such other place or places
designated by the Company and notified by it to the Holder of this Note.

               If less than the entire principal amount of the within Note is to
be repaid, specify the portion thereof which the Holder elects to have repaid
__________________ ___________________________________________; and specify the
denomination or denominations (which shall be authorized denominations) of the
Notes to be issued to the Holder for the portion of the within Note not being
repaid (in the absence of any specification, one such Note will be issued for
the portion not being repaid)_____________________.


Date: ______________


                                    ___________________________________________
                                    Note: The signature on this Option to Elect
                                    Repayment must correspond with the name as
                                    written in this Note in every particular
                                    without alteration or enlargement or any
                                    change whatsoever.