Cube 4 slices of bread and put in bottom of greased 9 x 13 glass pan. Mix together crab meat, Miracle Whip, and onion powder. Spread over bread. Cube remaining 4 slices of bread and put over crab mixture. Mix together one egg and milk and pour over all. Spread cream of mushroom over top and then top with cheddar cheese. Bake at 325 for 1 hour and 10 minutes. Cut into 9 servings.