Make 2 (1/2-inch-deep) diagonal cuts on each side of fish. Arrange fish in a large shallow dish.
Combine lemon juice and remaining ingredients. Set aside half of mixture to serve as a sauce with fish.
Brush inside of each fish with 1 tablespoon of lemon mixture. Pour remaining mixture over fish. Cover and chill 30 minutes, turning fish once.
Remove fish from marinade, reserving marinade; place fish in 2 lightly greased grill baskets.
Grill, covered with grill lid, over high heat (400° to 500°) 15 to 17 minutes on each side or until fish flakes with a fork, basting often with reserved marinade. On serving platter, tuck parsley and oregano around fish and surround with lemon wedges, if desired. Serve immediately with reserved sauce.