Mix orange juice, soy sauce, olive oil, chopped fresh parsley, lemon juice, minced garlic, chopped fresh oregano, and ground black pepper together in a large non-reactive dish until well combined.
Step 2
Place tuna steaks in marinade and turn to coat. Cover the dish with plastic wrap and marinate in the refrigerator for at least 30 minutes.
Step 3
Preheat an outdoor grill for high heat and lightly olive oil the grate.
Step 4
Remove tuna steaks from the marinade and shake off excess; reserve marinade for basting.
Step 5
Cook tuna steaks on the preheated grill for 5 to 6 minutes.
Step 6
Flip steaks and baste with reserved marinade. Cook for an additional 5 minutes, or to desired doneness.