Preheat oven to 350°F.
Combine crust ingredients cutting in butter with a pastry cutter or 2 knives. Mix until crumbly.
Press into a 13x9x2-inch baking pan. Bake for 15 minutes.
Mix together filling ingredients until well blended. Pour onto baked crust and bake for 20 minutes.
Combine topping ingredients using a pastry cutter to cut in butter. Sprinkle topping over pumpkin filling and bake an additional 20 minutes or until filling is set. Cool; cut into 3-inch squares. Serve with whipped cream or vanilla ice cream if desired.