In a large saucepan, heat oil over medium-high heat. Add onion and cook 4 minutes. Stir in eggplant and cook 5 minutes. Add garlic and cook 1 minute. Stir in yellow squash, zucchini, tomatoes, and salt and pepper. Bring mixture to boil, reduce heat and simmer 20 minutes or until veggies are tender. Stir in basil and vinegar, and serve with cooked pasta.