In mixing bowl, combine flour, oats, brown sugar, and baking soda.
Cut in margarine/butter until mixture resembles coarse crumbs.
Reserve ½ cup of the flour mixture.
Press remaining flour mixture into the bottom of an ungreased 9x9x2 baking pan.
Spread with desired filling.
Sprinkle with reserved flour mixture.
Bake at 350F for 30-35 minutes or until the top is golden.
Cool in pan on wire rack.
Cut into bars.
