Barbecued Shoulder of Beef

A beef shoulder (chuck) is as tough and flavorful a cut of meat as you are likely to grill. It benefits from marinating and requires long, slow cooking, but taking those precautions causes its fat to infuse the muscle fibers, flavoring them and separating one from another, and turning it into one of the tenderest and most succulent of grilled meats. This chuck is marinated with hot peppers and chiles and rubbed with a sweet, aromatic chile rub. Slice it as a roast or serve it shredded on a