how long to marinate tuna
1 Place the tuna steaks in the marinade and turn to coat. 2  Cover, and refrigerate for at least 30 minutes. 3  Preheat grill for high heat. 4  Lightly oil grill grate. 5  Cook the tuna steaks for 5 to 6 minutes, then turn and baste with the marinade. Preheat grill for high heat. 2  Lightly oil grill grate. 3  Cook the tuna steaks for 5 to 6 minutes, then turn and baste with the marinade. 4  Cook for an additional 5 minutes, or to desired doneness. 5  Discard any remaining marinade.