Cook beef and onion in 10-inch skillet over medium heat 8 to 10 minutes, stirring occasionally, until beef is brown; drain.
Mix beef, onion, salsa, chilies and chili powder in 3-1/2 to 4-quart slow cooker. Cover and cook on low heat setting 8 to 10 hours. Stir in beans. Cover and cook on low heat setting about 5 minutes or until hot. Top with cheese and onion.