In a bowl, mix together rolled oats, flour, and brown sugar. Cut in butter until a crumbly mixture is achieved. Put topping into refrigerator for 10-15 minutes to solidify butter again.
Preheat oven to 350 °F. In a small 8 x8 or 9 x 9 casserole dish, spread apple pie filling evenly. Crumble topping over filling.
Bake uncovered for 50- 60 minutes and until topping is golden brown. Remove from oven and let cool down for about 10 minutes before spooning apple crisp out of casserole dish.