Use 2 large pieces of heavy aluminum foil, overlapped. Place the fish in the center and season generously with salt and pepper. Place butter pieces on top of the cod, place the lemon slices on top and garnish with some fresh parsley.
Fold the foil around the fish and seal, creating a tent for the cod.
Using an outdoor grill that is heated to high (500 to 550 degrees), place the foil packet on the grill grates and close the grill. Grill for about 15 minutes.
Remove from oven, open carefully, serve and enjoy!
If your cod is larger in size, adjust the grill time accordingly.