Preheat oven to 350 degrees F. In large bowl, combine flour, oats, brown sugar and baking soda. Cut in butter until crumbly. Remove 3/4 cup of crumb mixture; stir in nuts and set aside. Firmly press remaining crumb mixture into a 13x9-inch baking pan.
Crumble mincemeat into medium saucepan; add sweetened condensed milk. Cook and stir over medium-low heat until thickened, about 5 minutes. Remove from heat.
Drop by small spoonfuls atop crust in pan; spread carefully to cover crust. Sprinkle with reserved crumb mixture; press down lightly.
Bake 40 minutes or until top is golden. Cool on wire rack. Cut into bars. Store loosely covered at room temperature.