Preheat oven to 350 Fahrenheit.
For the filling: In a small bowl, mix together the sugar, orange juice, corn starch, and cinnamon. Add to apples and mix well. Pour into pie crust.
For the crumb topping: In another bowl, mix flour, brown sugar and margarine with a fork, pastry cutter, or fingers until crumbs are about the size of peas. Add more flour or margarine to get desired consistency. Sprinkle over apples.
Place pie on a cookie sheet to catch any drips. Bake for 45 minutes to an hour or until top is nicely browned. If crust is browning too quickly, cover edges of pan with aluminum foil.