Heat oil in 4-quart Dutch oven over medium-high heat. Cook onions in oil 5 to 6 minutes, stirring frequently, until softened.
Stir in beef, garlic, salt and pepper. Cook about 13 minutes, stirring occasionally, until beef is lightly browned; drain. Place beef mixture in 6-quart slow cooker. Stir in chilies, cumin and broth.
Cover and cook on Low heat setting 8 to 9 hours.
Stir in bell peppers. Increase heat setting to High. Cover and cook 10 to 12 minutes or until bell peppers are hot. Serve with cheese.