Combine pineapple juice, vinegar, soy sauce, ginger, oil and garlic in a small bowl, mix well. Arrange tuna in glass or ceramic baking dish. Pour marinade over fish. Marinate in refrigerator, covered at least 30 minutes. Drain fish, reserving marinade. Place fish on oiled grid 4 to 5 inches from hot coals. Barbecue 6 minutes per inch of fish measured at its thickest point, basting frequently. Turn fish halfway through cooking time. Tuna should be pink in the center when removed from heat. Garnish with green onions, if desired.

Makes 4 servings