Rinse fish; pat dry with paper towels. Cut fish into 4 serving size pieces (this is easier if fish is slightly frozen). Place fish in a resealable plastic bag. Stir together lemon juice, olive oil, oregano, mint, garlic, lemon zest, and salt. Pour over fish. Seal bag. Turn to coat fish with marinade. Marinate in refrigerator for at least 30 minutes.
Drain fish, reserving marinade. Grill fish over medium heat for 8 to 12 minutes or until fish flakes easily when tested with a fork (145 degrees F), turning once and brushing with marinade halfway through grilling. Discard any remaining marinade.