Pat scallops and shrimp dry. Combine olive oil, lemon juice, garlic, parsley, basil and black pepper to make a marinade. Add shellfish and marinate 30 minutes to 1 hour, stirring occasionally. Alternate scallops, shrimp and mushrooms on skewers without crowding. Brush with marinade.
Broil or grill 10 cm from heat source for 4 minutes. Turn skewers, brush with marinade and continue to cook about 3 minutes more or until scallops and shrimp are opaque. Do not overcook. Serve with rice pilaf, if desired. Makes 4 servings.