In 3-quart saucepan, heat oil over medium-high heat. Add onion and garlic; cook 1 to 2 minutes, stirring frequently, until onion is crisp-tender.
Stir in all remaining ingredients. Heat to boiling. Reduce heat to low; cover and simmer 10 to 12 minutes, stirring occasionally, until vegetables are tender. If desired, season to taste with pepper.