In a large skillet over medium heat, heat the oil. Add the zucchini, onion, bell pepper, garlic, salt, and pepper. Cook, stirring, for 2 to 3 minutes. Cover and cook, stirring occasionally, until vegetables are just tender.
Cut the tomatoes into wedges and add to the skillet. Cover and cook for about 3 minutes longer, until tomatoes are heated.
Transfer to a serving dish and sprinkle with Parmesan cheese, if desired.
Calories per serving: 122
Fat per serving: 8.2