In 10-inch skillet, cook beef, onion and bell pepper over medium heat 8 to 10 minutes, stirring occasionally, until beef is brown; drain.
Stir in pizza sauce and olives. Heat to boiling, stirring occasionally.
Spoon about 1/2 cup beef mixture on bottom half of each bun. Immediately sprinkle each with 2 tablespoons of the cheese; add tops of bun. Serve immediately or let stand about 2 minutes until cheese is melted.