I found this recipe on a blog called Frugal Homekeeping.
Apple Crisp in the Crock Pot
6 cups cooking apples, peeled and sliced
1/2 cup quick-cook oats
1/2 cup brown sugar
1/2 cup flour
2 T. butter
1/2 tsp. cinnamon
Place apples in greased crock pot. Combine remaining ingredients in mixing bowl until crumbly. Sprinkle over apples. Cover. Cook on low for 4 hours or high for 2 hours.