Fire up your grill for indirect cooking at 350 F.
Place crab legs in a disposable aluminum pan. If the legs are too long you may have to cut them at the joints to make them fit.
Melt the butter.
Add the garlic.
Stir in the lemon juice and cook for 5 minutes.
Pour mixture over the crab legs.
Sprinkle with the Old Bay and toss to coat.
Transfer to the grill and cook for 20-30 minutes or until the crab is done, basting occasionally.
Grill the lemon quarters while you are cooking the crab legs and then transfer to the pan with the crab.
Remove crab legs to a platter and transfer any remaining drippings to a bowl for dipping.