Place tuna steaks in resealable food storage plastic bag. Add all remaining ingredients. Seal bag; turn to mix well. Refrigerate at least 30 minutes.
Heat grill. Place tuna on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals; discard marinade. Cook 6 to 7 minutes or until fish is firm but still pink inside and flakes easily with fork, turning once.