Heat oil in medium pot. Add onion, garlic, chili powder and cumin. Saute over medium heat until onion is soft, about 5 minutes. Add remaining ingredients (except garnishes) and stir. Bring to a boil, then lower heat and simmer 20 minutes or until vegetables are soft. Add more liquid if needed.
Serve alone or over rice (preferably brown). Garnish if desired with any of the following: reduced-fat cheddar cheese, onion, fat-free sour cream, guacamole, fresh cilantro.