1Heat coals or gas grill for direct heat.
2Mix lemon juice, oil, thyme, salt and pepper. Cut scallops in half if over 1 inch in diameter.
3Thread scallops, shrimp, mushrooms, tomatoes and zucchini alternately on each of four 10-inch metal skewers. Brush with lemon juice mixture.
4Grill uncovered 4 inches from medium heat 10 to 15 minutes, brushing frequently with lemon juice mixture and turning once, until scallops are white and shrimp are pink and firm.