For CRUMB TOPPING: Combine flour and brown sugar in small bowl; Cut in butter using pastry blender or 2 knives until coarse crumbs form. Stir in nuts if desired. Set topping aside.
Preheat oven to 400°F.
For APPLE PIE FILLING: Combine sugar, corn starch and cinnamon in a large bowl. Add apples and lemon juice; toss to coat.
Unfold pie crust; place on foil-lined cookie sheet. Spoon APPLE PIE FILLING into center of crust, leaving 2-inch edge. Sprinkle CRUMB TOPPING over apples. Fold up edge of crust, pinching at 2-inch intervals.
Bake 15 minutes at 400°F. Reduce temperature to 350°F; bake 35 minutes longer or until apples are tender.