Wanda'S Cheese Potatoes
["5 lb. potatoes, peeled and sliced (not too thin)", "2 medium onions, sliced", "1 small jar Cheez Whiz", "1 small can evaporated milk", "1 stick margarine", "1 piece Cheddar or Colby cheese (approximately 1 lb.)"]
["Bring potatoes and onions to a boil; let boil about 5 minutes. Do not overcook, as potatoes will become mushy.", "Drain in colander."]
["potatoes", "onions", "milk", "margarine", "Cheddar"]