Heat oven to 350°F. Grease 9-inch glass pie pan. Prepare potatoes as directed on package using water, milk, 3 tablespoons of the butter and salt.
Meanwhile, melt remaining 1 tablespoon butter in medium skillet over medium heat. Add bell pepper, onions and cilantro; cook 3 minutes or until tender, stirring occasionally.
Add vegetable mixture to potatoes. Stir in egg and 1/2 cup of the cheese. Spoon into greased pan; spread evenly. Sprinkle with remaining 1/4 cup cheese.
Bake at 350°F. for 18 to 25 minutes or until potatoes are thoroughly heated and edges begin to look dry.