Heat oven to 425°F. Crush cereal. (To easily crush cereal, place in plastic bag or between sheets of waxed paper, and crush with rolling pin.) In large bowl, mix crushed cereal, beef, rice, milk, dry soup mix and egg. Using wet hands, shape mixture into 30 meatballs. Place in ungreased 13x9-inch baking dish or 3-quart casserole.