Preheat gas grill or contact grill.

Lightly brush bell peppers and eggplants with oil and grill on an oiled rack about 4 minutes on each side, or until cooked through. Cut peppers into strips.

Lightly brush cut sides of bread with oil and grill, cut sides down, about 2 minutes, or until golden. Spread each piece of bread with 4 tablespoons pesto and divide peppers, eggplants, and mozzarella between them.

Grill sandwiches (or broil), covered, just until cheese is melted. Cut sandwich in half.