In a large bowl combine orange juice, olive oil, oregano, parsley, salt and pepper. Mix well. Place the tuna steaks in the bowl, turn to coat both sides with marinade; cover and refrigerate 30 minutes.
Preheat barbecue for medium-high heat.
Remove tuna from the marinade and shake off excess. Place tuna onto preheated barbecue and cook to desired doneness, about 5-10 minutes.