Heat oven to 400°. Brown ground beef in large nonstick skillet over medium heat 6 minutes. Add onion and bell pepper; cook until beef is not pink and vegetables are crisp-tender, breaking beef up into small crumbles. Pour off drippings; season with salt and pepper. Place pizza crust on baking sheet. Top with beef mixture, then cheese. Bake in 400° oven 8 to 10 minutes or until cheese is melted.