Cherry Crumble

1 package yellow cake mix
1/2 cup (1 cube) margarine
1/4 cup packed brown sugar
1/2 cup quick oats
1 tsp. cinnamon
1-1/2 cans cherry pie filling
1 cup sour cream
1 egg

Heat oven to 350 degrees.  Mix dry cake mix, margarine, brown sugar, oats, and cinnamon until crumbly. Reserve 2/3 cup mixture.  Press remaining mixture on bottom of greased 9x13" baking dish.  Spread cherry pie filling on mixture in pan.  Beat sour cream and egg until blended; spread over cherries.  Sprinkle with reserved mixture.  Bake 35-40 min or until topping is set.  Let cool a bit.  Serve warm with ice cream or drizzled with half-and-half. Cover and refrigerate any remaining dessert.