To grill halibut you need to oil the cooking grates before adding the fish to the fire. Otherwise it will stick and there’s no way to get it up cleanly. You can marinate it in a mild lemon juice mixture for a little while before grilling. Grill it for about 5 minutes on each side if it’s a medium sized piece of halibut. A full halibut will cook in about 10 minutes on medium heat!