Heat oil in 4-quart pot over medium heat. Add onion, garlic and chili powder; sauté for 5 minutes. Add green and red peppers; sauté 5 minutes. Add zucchini, squash, oregano and ground red pepper; sauté for 5 minutes. Add tomatoes; cook 10 minutes. Stir in corn, black beans and salt; cook for 5 minutes.
Serve with the accompaniments, if desired.