Sauté onion in hot oil in a large nonstick skillet over medium-high heat 5 minutes or until crisp-tender. Add eggplant and squash. Cover and cook, stirring occasionally, 10 minutes or until eggplant begins to soften. Stir in tomatoes and remaining ingredients. Cover and cook 5 more minutes.
Delicious combo of summer veggies. I have made this several times and even served it to guests with great success.