1Heat oven to 350°F. Spray rectangular baking dish, 11x7x1 1/2 inches, with cooking spray.
2Make potatoes as directed on pouch, using water, milk and butter. Spread half of the potatoes over bottom of baking dish. Layer with beef, 1 cup of the cheese and remaining potatoes.
3Cover with aluminum foil and bake about 30 minutes or until hot. Sprinkle with remaining 1/2 cup cheese. Sprinkle onions around edges of baking dish. Bake uncovered 3 to 4 minutes longer or until cheese is melted and onions are brown.