Prepare a charcoal (or gas) grill. In a small bowl, mix first five ingredients until combined. Arrange oysters in a cast- iron pan and top each with ½ teaspoon compound butter. Grill over high heat, covered, until oysters are barely cooked through, about five minutes. Sprinkle lemon zest over top. Serve with lemon quarters and grilled bread. From Don't Forget the Oysters.