Combine in a large bowl the quick cooking rolled oats,sifted flour, brown sugar, teaspoon salt, and cinnamon.
Add butter chunks and cut in until mixture is in fine crumbs.
Pat two-thirds of crumb mixture into a greased 9-square pan. (Only alteration in our household, after inheriting this recipe, is todivide the crumb mixture in half, rather than the ⅔ , ⅓ specified in Moms directions; usehalf on bottom, remaining half on top of mincemeat layer.)
Spoon evenly over top, one 1 pound 2 ounce jar (1 ¾ cups) mincemeat. If adding nuts, add chopped nuts into the remaining crumb mixture;sprinkle over mincemeat.
Bake at 350° F. for 40 minutes.
Cool in pan.
Cut into squares.