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 basket occasionally to turn vegetables, until bell pepper and onion are crisp-tender and mushrooms are just tender.
3Cut bread horizontally in half. Mix mayonnaise and pesto; spread over cut sides of bread. Layer lettuce and grilled vegetables on bottom half of bread. Add top of bread. Cut into 6 wedges.