HEAT oven to 350°. Coat 15 x 10 x 1-inch baking pan with no-stick cooking spray.
BEAT butter, sugar and brown sugar in extra-large bowl with mixer on high speed until light and fluffy.
ADD flour, oats, cinnamon and salt. Mix on low speed until blended.
MEASURE 2 1/2 cups dough; chill until later use. Press remaining dough firmly into prepared pan to form a crust. Bake 15 minutes.
REMOVE pan from oven. Spoon mincemeat over crust, spreading evenly. Sprinkle evenly with nuts. Finely crumble reserved dough over top.
BAKE 30 minutes or until edges and topping are lightly browned. Cool completely in pan on wire rack.