In a Dutch oven over medium-high heat, saute onion in oil for 3 minutes or until tender. Add garlic; cook 1 minute longer. Stir in the remaining ingredients. Bring to a boil over medium-high heat. Reduce heat; cover and simmer for 15-20 minutes or until vegetables are crisp-tender.
Serve immediately or transfer to freezer containers. May be frozen for up to 3 months.
To use frozen soup: Thaw soup in the refrigerator overnight. Transfer to a saucepan. Cover and cook over medium heat until heated through.