Put sauerkraut in bottom of baking dish.  Top with corned beef and onion.  Next, top with slices of Swiss cheese.  Combine Miracle Whip and Thousand Island dressing together and spread over the chesse.  Mix cubed bread with melted butter and sprinkle over the top.  Bake in a 350 degree oven until done. If you like Reuben sandwiches, this is the same thing, only baked.