Heat a large Dutch oven over high heat. Add oil. When oil is hot, add onion, zucchini, yellow squash, red and yellow peppers, eggplant and garlic. Cook until softened, about 12 minutes, stirring often.

Add tomatoes, tomato paste, sugar, vinegar, basil, salt, and pepper.

Cover, reduce heat to low, and simmer 20 minutes or until vegetables are cooked through but not mushy.

Serve warm or at room temperature.