1. Heat oven to 350°F. Spray 13 x 9-inch (3-quart) glass baking dish with cooking spray
2. In large bowl, mix potatoes, sauce mix (from both potato mixes) and boiling water. Stir in sour cream, milk, margarine, bell pepper and 1/4 cup of the onions. Spoon into baking dish.
3. Bake uncovered 35 minutes Sprinkle with remaining onions and the cheese. Bake 5 to 10 minutes longer or until bubbly around edges and potatoes are tender. Let stand 5 minutes before serving.