In a large skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Stir in the beans, chilies, and garlic powder; heat through.
Combine the sour cream, cumin, and chili powder; spread over beef mixture. Top with tomato, olives, and green peppers. Sprinkle with cheese. Serve with tortilla chips or taco shells, lettuce, and salsa.