Exhibit 5.1

                OPINION AS TO LEGALITY OF SHARES BEING REGISTERED

                          Katten Muchin Zavis Rosenman

                        1025 Thomas Jefferson Street, NW
                              East Lobby, 7th Floor
                              Washington, DC 20007
                                  202 625-3500


                                November 3, 2003

First Midwest Financial, Inc.
Fifth at Erie
Storm Lake, IA 50588

Ladies and Gentlemen:

We  have  acted  as  counsel  to  First  Midwest  Financial,  Inc.,  a  Delaware
corporation (the "Company"),  in connection with the preparation and filing with
the  Commission  of a  Registration  Statement  on Form S-8  (the  "Registration
Statement"), pursuant to which the Company is registering the issuance under the
Securities  Act of 1933,  as  amended,  of a total of  200,000  shares  (the
"Shares") of its common  stock,  $.01 par value per share (the  "Common  Stock")
under the Company's 2002 Omnibus  Incentive  Plan (the "Plan").  This opinion is
being rendered in connection with the filing of the Registration Statement.  All
capitalized  terms  used  herein  and  not  otherwise  defined  shall  have  the
respective meanings given to them in the Registration Statement.

In connection with this opinion,  we have examined the Company's  Certificate of
Incorporation and Bylaws, both as currently in effect; such other records of the
corporate  proceedings of the Company and certificates of the Company's officers
as we have deemed  relevant;  and the  Registration  Statement  and the exhibits
thereto.

In our examination, we have assumed the genuineness of all signatures, the legal
capacity of natural persons,  the authenticity of all documents  submitted to us
as originals, the conformity to original documents of all documents submitted to
us as certified or photostatic  copies and the  authenticity of the originals of
such copies.

Based upon the  foregoing,  we are of the opinion  that (i) the Shares have been
duly and validly  authorized  by the  Company and (ii) the Shares,  when sold in
accordance  with the  provisions  of the Plan,  will have been duly and  validly
issued,  fully  paid and  non-assessable  shares of the  Common  Stock,  free of
preemptive rights.

Our opinion is limited to the General Corporation Laws of the State of Delaware,
and we express no opinion with respect to the laws of any other jurisdiction. No
opinion is  expressed  herein with  respect to the  qualification  of the Shares
under the securities or blue sky laws of any state or any foreign jurisdiction.

We  understand  that  you  wish  to  file  this  opinion  as an  exhibit  to the
Registration Statement, and we hereby consent thereto.

                                                      Very truly yours,

                                               /s/  Katten Muchin Zavis Rosenman
                                               ---------------------------------
                                                    Katten Muchin Zavis Rosenman