Brown ground beef in oil in a large skillet. Add onions and green pepper; cook until onions are tender. Stir in tomatoes, corn, olives, and chili powder; cover and simmer 10 min. Meanwhile, prepare stuffing as directed on package, using 1½ cups water. Stir half the cheese into meat mixture. Spoon into 2½ qt. baking dish, spoon stuffing around edge of dish and sprinkle remaining cheese in a ring near stuffing. Bake at 400° uncovered, for 30 min. or until hot and bubbly. Garnish with additional ripe olives, if desired. Makes 6 servings.