UNITED STATES
                             SECURITIES AND EXCHANGE COMMISSION
                                   WASHINGTON, D.C. 20549



                                          FORM 10-K


  (Mark one)

  /X/ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934
      For the fiscal year ended December 31, 2005

      OR



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


      Commission File Number:  333-106982-69


        MASTR Asset Backed Securities Trust
        Mortgage Pass-Through Certificates
        Series 2005-OPT1

     (Exact name of registrant as specified in its charter)


  New York                                          54-2175560
  (State or other jurisdiction of                   54-2175561
  incorporation or organization)                    54-2175562
                                                    54-2175563
                                                    (I.R.S. Employer
                                                    Identification No.)


   c/o Wells Fargo Bank, N.A.
   9062 Old Annapolis Road
   Columbia, MD                                21045
  (Address of principal executive offices)    (Zip Code)


  Registrant's telephone number, including area code: (410) 884-2000


  Securities registered pursuant to Section 12(b) of the Act:

        NONE.


  Securities registered pursuant to Section 12(g) of the Act:

        NONE.


  Indicate by check mark if the registrant is a well-known seasoned issuer,
  as defined in Rule 405 of the Securities Act.

        Yes  ___     No  X


  Indicate by check mark if the registrant is not required to file reports
  pursuant to Section 13 or Section 15(d) of the Act.

        Yes  ___     No  X


  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.

        Yes  X       No  ___


  Indicate by check mark if disclosure of delinquent filers pursuant to
  Item 405 of Regulation S-K ( 229.405 of this chapter) is not contained
  herein, and will not be contained, to the best of registrant's knowledge,
  in definitive proxy or information statements incorporated by reference
  in Part III of this Form 10-K or any amendment to this Form 10-K.

        Not applicable.


  Indicate by check mark whether the registrant is a large accelerated filer,
  an accelerated filer, or a non-accelerated filer. See Definition of
  "accelerated filer and large accelerated filer" in Rule 12b-2 of the
  Exchange Act. (Check One):


  Large Accelerated Filer ___  Accelerated Filer ___  Non-Accelerated Filer X


  Indicate by check mark whether the registrant is a shell company (as
  defined in Rule 12b-2 of the Act).

        Yes  ___     No  X


  State the aggregate market value of the voting and non-voting common
  equity held by non-affiliates computed by reference to the price at which
  the common equity was last sold, or the average bid and asked price of
  such common equity, as of the last business day of the registrant's most
  recently completed second fiscal quarter.

        Not applicable.


     Documents Incorporated by Reference

  List hereunder the following documents if incorporated by reference and
  the Part of the Form 10-K (e.g. Part I, Part II, etc.) into which the
  document is incorporated: (1)Any annual report to security holders; (2)
  Any proxy or information statement; and (3)Any prospectus filed pursuant
  to Rule 424(b) or (c) under the Securities Act of 1933. The listed
  documents should be clearly described for identification purposes (e.g.
  annual report to security holders for fiscal year ended December 24, 1980).

        Not applicable.


                                   PART I
  Item 1.  Business.

            Not applicable.


  Item 1A.  Risk Factors.

            Not applicable.


  Item 1B.  Unresolved Staff Comments.

            Not applicable.


  Item 2.  Properties.

            Not applicable.


  Item 3.  Legal Proceedings.

            The registrant knows of no material pending legal proceedings
            involving the trust created under the Pooling and Servicing
            Agreement (the Trust), the Trustee, the Servicer or the
            registrant with respect to the Trust other than routine
            litigation incidental to the duties of the respective parties.


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

            None.

                                PART II

  Item 5.  Market for Registrant's Common Equity, Related Stockholder
           Matters and Issuer Purchases of Equity Securities.

            No established public trading market for the Certificates exists.

            Records provided to the Trust by the DTC and the Trustee
            indicate that as of December 31, 2005, the total number of holders
            of record for the Series of Certificates is 37.


  Item 6.  Selected Financial Data.

            Not applicable.

  Item 7.  Management's Discussion and Analysis of Financial Condition and
           Results of Operation.


            Not applicable.


  Item 7A. Quantitative and Qualitative Disclosures about Market Risk.

            Not applicable.


  Item 8.  Financial Statements and Supplementary Data.

            Not applicable.


  Item 9.  Changes in and Disagreements with Accountants on Accounting and
           Financial Disclosure.

            None.


  Item 9A. Controls and Procedures.

            Not applicable.


  Item 9B. Other Information.

            None.


                                PART III

  Item 10. Directors and Executive Officers of the Registrant.

            Not applicable.


  Item 11. Executive Compensation.

            Not applicable.

  Item 12. Security Ownership of Certain Beneficial Owners and Management
           and Related Stockholder Matters.

            Not applicable.

  Item 13. Certain Relationships and Related Transactions.

            Not applicable.


  Item 14. Principal Accounting Fees and Services.

            Not applicable.


                                PART IV

  Item 15. Exhibits, Financial Statement Schedules.

   (a) Exhibits

     (31.1) Rule 13a-14(a)/15d-14(a) Certification

     (99.1) Annual Independent Accountants' Servicing Reports concerning
            servicing activities.

      <TABLE>

      
         <c>
      a) Option One Mortgage Corporation, as Servicer <F1>

      </TABLE>

     (99.2) Report of Management as to Compliance with Minimum Servicing
            Standards.

      <TABLE>

      
        <c>
      a) Option One Mortgage Corporation, as Servicer <F1>

      </TABLE>

     (99.3) Annual Statements of Compliance under the Pooling and Servicing
            Agreements.

      <TABLE>

      
         <c>
      a) Option One Mortgage Corporation, as Servicer <F1>

      </TABLE>


     (99.4) Aggregate Statement of Principal and Interest Distributions to
            Certificate Holders.


   (b) Not applicable.

   (c) Omitted.


  <F1> Filed herewith.


                                SIGNATURES

  Pursuant to the requirements of Section 13 or 15(d) 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:



    MASTR Asset Backed Securities Trust
    Mortgage Pass-Through Certificates
    Series 2005-OPT1
    (Registrant)


  Signed: Option One Mortgage Corporation as Master Servicer

  By:     William L. O'Neill, Senior Vice President/
          Chief Financial Officer

  By: /s/ William L. O'Neill, Senior Vice President/
          Chief Financial Officer

  Dated:  March 24, 2006


  Exhibit Index

  Exhibit No.

  Ex-31.1 Rule 13a-14(a)/15d-14(a) Certification

  MASTR Asset Backed Securities Trust 2005-OPT1

  Mortgage Pass Through Certificates, Series 2005-OPT1

  I, William L. O'Neill, certify that:

  1. I have reviewed this annual report on Form 10-K, and all reports on
     Form 8-K containing distribution or servicing reports filed in
     respect of periods included in the year covered by this annual report,
     of MASTR Asset Backed Securities Trust 2005-OPT1, Mortgage Pass Through
     Certificates, Series 2005-OPT1;

  2. Based on my knowledge, the information in these reports, taken as a
     whole, does not contain any untrue statement of a material fact or
     omit to state a material fact necessary to make the statements made,
     in light of the circumstances under which such statements were made,
     not misleading as of the last day of the period covered by this annual
     report;

  3. Based on my knowledge, the distribution or servicing information
     required to be provided to the trustee by the servicer under the
     pooling and servicing, or similar, agreement, for inclusion in these
     reports is included in these reports;

  4. Based on my knowledge and upon the annual compliance statement
     included in the report and required to be delivered to the trustee in
     accordance with the terms of the pooling and servicing, or similar,
     agreement, and except as disclosed in the reports, the servicer has
     fulfilled its obligations under the servicing agreement; and

  5. The reports disclose all significant deficiencies relating to the
     servicer's compliance with the minimum servicing standards based upon
     the report provided by an independent public accountant, after
     conducting a review in compliance with the Uniform Single Attestation
     Program for Mortgage Bankers or similar procedure, as set forth in the
     pooling and servicing, or similar, agreement, that is included in these
     reports.

     In giving the certifications above, I have reasonably relied on
     information provided to me by the following unaffiliated parties:
     Wells Fargo Bank, N.A. as Trustee.


     Date: March 24, 2006

     /s/ William L. O'Neill
     Signature

     Senior Vice President/Chief Financial Officer
     Title


  EX-99.1
(logo) KPMG

KPMG LLP
Suite 2000
355 South Grand Avenue
Los Angeles, CA 90071-1568


Independent Accountants' Report

The Board of Directors and Stockholder
Option One Mortgage Corporation:

We have examined management's assertion, included in the accompanying management
assertion, that Option One Mortgage Corporation complied with the minimum
servicing standards set forth in the Mortgage Bankers Association of America's
Uniform Single Attestation Program for Mortgage Bankers as of and for the year
ended December 31, 2005. Management is responsible for Option One Mortgage
Corporation's compliance with those minimum servicing standards. Our
responsibility is to express an opinion on management's assertion about the
Company's compliance based on our examination.

Our examination was conducted in accordance with attestation standards
established by the American Institute of Certified Public Accountants and,
accordingly, including examining, on a test basis, evidence about Option One
Mortgage Corporation's compliance with the minimum servicing standards specified
above and performing such other procedures as we considered necessary in the
circumstances. We believe that our examination provides a reasonable basis for
our opinion. Our examination does not provide a legal determination on Option
One Mortgage Corporation's compliance with the minimum servicing standards.

In our opinion, management's assertion that Option One Mortgage Corporation
complied with the aforementioned minimum servicing standards as of and for the
year ended December 31, 2005 is fairly stated in all material respects.

/s/ KPMG LLP

Los Angeles, California
February 28, 2006

KPMG LLP, a U.S. limited liability partnership, is the U.S.
member firm of KPMG International, a Swiss cooperative.





  EX-99.2
(logo) OPTION ONE
       MORTGAGE
       an H&R BLOCK company

(logo) H&R BLOCK

Management Assertion

As of and for the year ended December 31, 2005, Option One Mortgage Corporation
Complied in all material respects with the minimum servicing standards set forth
in the Mortgage Bankers Association of America's Uniform Single Attestation
Program for Mortgage Bankers. As of and for this same period, Option One
Mortgage Corporation had in effect a fidelity bond and errors and omissions
policy in the amounts of $70,000,000 and $10,000,000, respectively.

/s/ Robert E Dubrish
Robert E. Dubrish, Chief Executive Officer

/s/ William L. O'Neill
William L. O'Neill, Chief Financial Officer

/s/ Matthew A. Engel
Matthew A. Engel, Controller

/s/ Fabiola Camperi
Fabiola Camperi, Chief Servicing Officer



www.optiononeonline.com





  EX-99.3
(logo) Option One Mortgage
an H&R Block Company



OFFICER'S CERTIFICATE

ANNUAL STATEMENT OF THE SERVICER

I, Fabiola Camperi, the duly appointed Chief Servicing Officer of Option One
Mortgage Corporation, the Servicer, hereby certify that (i) a review of the
activities of the Servicer during the calendar year ended December 31, 2005 and
of performance under the Servicing Agreement, as defined in the cover letter,
has been made under my supervision, and (ii) to the best of my knowledge, based
on such review, the Servicer has fulfilled all of its obligations under the
Servicing Agreement during such year.


By: /s/ Fabiola Camperi

Name: Fabiola Camperi
Title: Chief Servicing Officer
Date: February 28, 2006


6501 Irvine Center Drive * Irvine * Californa * 92618-2304 * 949-790-3600





  Ex-99.4

   Schedule of Year-To-Date Principal and Interest Distributions to
   Certificateholders


   <TABLE>

   Class                              Interest             Principal               Losses             Ending Balance
   
                       <c>                    <c>                  <c>                 <c>
   A-1                           14,739,032.15        182,126,694.07                 0.00             484,683,305.94
   A-2                            1,618,752.20         20,236,572.47                 0.00              53,854,427.53
   A-3                            5,956,844.15        150,187,551.87                 0.00             166,424,448.13
   A-4                            5,988,422.73                  0.00                 0.00             247,690,000.00
   A-5                            1,140,483.89                  0.00                 0.00              45,612,000.00
   CE                            15,343,102.20                  0.00                 0.00              11,216,730.25
   M-1                            1,188,515.85                  0.00                 0.00              46,469,000.00
   M-10                             311,946.14                  0.00                 0.00               8,012,000.00
   M-11                             326,629.30                  0.00                 0.00               7,211,000.00
   M-2                              967,900.55                  0.00                 0.00              37,656,000.00
   M-3                              644,723.76                  0.00                 0.00              24,837,000.00
   M-4                            1,029,082.14                  0.00                 0.00              39,259,000.00
   M-5                              365,680.02                  0.00                 0.00              13,620,000.00
   M-6                              416,465.38                  0.00                 0.00              15,223,000.00
   M-7                              532,251.17                  0.00                 0.00              18,427,000.00
   M-8                              423,908.70                  0.00                 0.00              14,422,000.00
   M-9                              520,079.06                  0.00                 0.00              15,223,000.00
   P                              5,084,149.87                  0.00                 0.00                     100.00
   </TABLE>