In shallow dish, combine all ingredients for marinade.
Add zucchini, yellow squash, eggplant and onion. Marinate for about one hour.
Remove vegetables from marinade, reserving two teaspoons for later use.
In non-stick fry pan or wok, quickly stir-fry vegetables until tender-crisp.
Split baguette and distribute vegetables evenly over bottom half.
Top with tomatoes and cheese. Drizzle reserved marinade over sandwich.
Cover with baguette top and secure with toothpicks.