Place margarine in 9x13 inch baking dish and put in oven to melt. When margarine is completely melted, pour in macaroni, salt and pepper. Stir until macaroni is coated with butter. Sprinkle cheese over macaroni and add slices of velvetta and then pour milk over all. Do not stir and do not cover dish.
Bake in preheated oven for 60 minutes. Do not stir while baking.