Thaw steaks if frozen. Cut into serving-size portions and place in a single layer in a shallow baking dish. Combine remaining ingredients. Pour sauce over steaks and refrigerate 30 minutes, turning once. Tuna should have a pink center.
Remove fish, reserving sauce for basting. Place fish in well-greased, hinged wire grills. Cook about 4 inches from moderately hot coals 5 to 6 minutes. Baste with sauce. Turn and cook for 4 to 5 minutes longer or until steak reaches 140 degrees, internally.