Heat oven to 325°F. In large skillet, cook beef in oil over medium-high heat until lightly browned. Add onions and bell pepper; cook and stir 4 to 5 minutes or until vegetables are crisp-tender and beef is no longer pink. Stir in sauce. Cook until thoroughly heated. Spoon into ungreased 12x8-inch (2-quart) baking dish.
In medium saucepan, bring water, margarine and garlic to a boil. Remove from heat; add milk. Stir in potato flakes and cheese. Add egg; blend well. Spoon or pipe potato mixure around edges of baking dish over hot beef mixture.
Bake at 325°F. for 25 to 35 minutes or until potatoes are set and light golden brown.