Preheat oven to 375°. In a large bowl, combine oats, flour, brown sugar and butter; set aside 3/4 cup for topping. Press remaining mixture onto the bottom and up the sides of a greased 9-in. pie plate. Bake 13-17 minutes or until lightly browned.
In another bowl, combine pie filling, cranberries, lemon juice and cinnamon. Spoon into crust. Sprinkle with reserved oat mixture.
Bake 25-30 minutes or until topping is lightly browned. Cool on a wire rack. Serve with ice cream if desired.