Preheat a gas grill for low heat.
Cover the turkey with butter, inside and out.
Continue to spread butter all over chicken base.
Slice remaining butter into cubes.
Add onions, apples, garlic, and butter cubes into a large bowl.
Stuff turkey with butter mixture.
Transfer bird to an aluminum roasting pan.
Fold the turkey skin around the neck, flip turkey over and pour wine into the opening.
Set the turkey breast side up.
Add the roasting pan onto the preheated grill and cover loosely with aluminum foil.
Cover with the lid.
Roast 4 hours.
During the final minutes of cooking, remove the aluminum foil.
Set aside for 20 minutes before carving.