Preheat oven to 425 degrees F. Combine flour and sugars; cut in butter until crumbly. Stir in nuts. Reserving 1 1/2 cups crumb mixture press remaining crumb mixture on bottom and halfway up sides of 13x9-inch baking dish. Spoon mincemeat over crust.
Combine remaining ingredients except reserved crumb mixture; mix well. Pour over mincemeat. Top with reserved crumb mixture.
Bake 15 minutes; reduce oven to 350 degrees F. Bake 40 minutes longer or until golden brown around edges. Cool. Cut into squares. Serve warm or at room temperature. Store leftovers covered in refrigerator.