1Heat gas or charcoal grill. Brush mushrooms, bell pepper and onion with oil. Sprinkle with seasoned salt. Place vegetables in grill basket (grill "wok").
2Place grill basket on grill over medium heat. Cover grill; cook 10 to 12 minutes, shaking grill basket occasionally to turn vegetables, until bell pepper and onion are crisp-tender and mushrooms are just tender.
3Cut bread horizontally in half. In small bowl, mix mayonnaise and pesto; spread over cut sides of bread. Layer lettuce and grilled vegetables on bread bottom. Cover with bread top top. Cut into 6 wedges.