Brush zucchini, yellow squash, and red pepper halves with olive oil. Sprinkle with black pepper and salt. Preheat gas grill. Reduce heat to medium. Place vegetables on the grill rack directly over heat. Cover and grill for 6 to 8 minutes or until vegetables are crisp-tender, turning once halfway through grilling. Remove from grill; cool slightly.
Chop the grilled vegetables. In a medium bowl combine chopped vegetables, tomato, mayonnaise, pesto, basil, and oregano. Place tortillas on the grill rack directly over heat. Cover and grill for 1 to 2 minutes or until lightly toasted on one side. Turn tortillas over and spread the vegetable mixture over the toasted sides of tortillas. Sprinkle with shredded cheese.
Cover and grill for 2 to 3 minutes more or until tortillas are lightly toasted, vegetables are just heated, and cheese begins to melt. Carefully remove from grill. To serve, cut into quarters. Makes 8 servings.