Prepare the grill: Coat the rack with cooking spray, or use tongs to dip a large piece of paper towel into vegetable oil and rub it on the grill rack. (Discard the towel.) Set a gas grill to medium heat, or prepare a medium fire on a charcoal grill.
Peel, core, and halve the pineapple. Wrap one half of the pineapple and store for another use. Slice the remaining half of pineapple into 8 slices.
In a small saucepan, combine the maple syrup and butter, and cook over low heat until the butter melts.
Place the pineapple slices on the grill, and baste with some of the maple butter. Grill on one side for about 8 to 10 minutes. Turn the pineapple, basting with maple butter, and continue to grill for another 8 to 10 minutes or until the pineapple is golden brown.