I think the sauce really makes this sandwich what it is. The bread helps, too. This recipe is slightly adapted from a highly-rated one I got on All Recipes. The original calls for foccacia bread which I've tried and is good. I prefer (homemade) ciabatta because the flavor of the sauce and veggies really comes out that way. You can also switch up the veggies (add mushroom or eggplant) and cheeses (feta, provolone, parmesan...) to suit your desires.
1/4 cup light mayonnaise
3 cloves garlic, minced
1 tablespoon lemon juice
1 T. olive oil
1 red bell peppers, sliced
2 small zucchini, sliced
1 red onion, sliced
1 small yellow squash, sliced
Good bread (foccacia, ciabatta, etc...)
Your choice of cheese (optional; I've used Parmesan and Provolone)
1. In a bowl mix sauce ingredients (mayo, garlic, lemon juice); refrigerate until ready to use.
2. Preheat grill or broiler.
3. In a separate bowl, toss veggies with olive oil until all are coated.
4. Grill or broil, turning as necessary and watching carefully until veggies are done to your likely.
5. Assemble sandwich: put sauce on bread, top with veggies, add cheese (if desired).
6. Enjoy the vegetarian goodness!