Spray 13x9-inch (3-quart) glass baking dish with nonstick cooking spray. Sprinkle half of cheese evenly into sprayed baking dish.
Melt margarine in medium skillet over medium heat. Add onions, 1/2 medium bell pepper and mushrooms; cook until onions and bell pepper are tender. Arrange vegetables over cheese in baking dish. Top with ham strips. Sprinkle remaining cheese over ham.
Beat eggs in large bowl. Lightly spoon flour into measuring cup; level off. Add flour, parsley and milk to eggs; blend well. Pour over mixture in baking dish. Cover; refrigerate 8 hours or overnight.
To serve, heat oven to 350°F. Uncover baking dish; bake at 350°F. for 55 to 65 minutes or until mixture is set and top is lightly browned. Let stand 10 minutes before serving. To serve, cut into squares. Garnish with red bell pepper and fresh parsley.