Preheat oven to 350 degrees.
Sprinkle marshmallows in a greased 13 x 9 inch pan.
Prepare cake according to package directions; pour over marshmallows.
Spoon pie filling over the batter.
Bake 1 hour or until a toothpick inserted near the center comes out clean.
Cool. Frost with whipped topping.
Store in the refrigerator.