1. Spread pie filling into an ungreased 1-1/2 quart casserole dish and place into the oven. Preheat oven to 400 and remove pan.
2. While oven is heating, add bisquick and sugar in a bowl and mix well. Use a fork to blend in butter. Stir in milk. Spoon on top of apples and sprinkle with coarse sugar if using.
3. Return to oven and bake for 15-18 minutes or until top is browned. Remove from oven and serve warm.