Chuck steak isn't a cut that's usually used for grilling, so a little extra effort to get it grill-ready goes a long way. It's richly flavorful and well-marbled, but most chuck steaks are just too tough and chewy to be pleasurable without long, slow cooking. If you're partial to grilled steaks but like chuck because of its good flavor and budget-friendly price, a small amount of tenderizing can help you bridge that gap.
Inside the Shoulder
The chuck, or beef shoulder, is a complicated cut. It has to support the steer's movements in any direction, so it contains a large number of small muscles running at different angles. It's also a well-used group of muscles, which is why they're dense, tough and filled with connective tissue. Making a chuck steak tender enough for grilling requires loosening and shortening the strands of proteins in the muscle, so your teeth can penetrate them. You can break them down either physically or chemically, depending on the texture and flavor you're looking for.
The "Marinating Steak" Fallacy
You'll often see chuck steaks sold as "marinating steaks," in accordance with the time-honored wisdom that an acidic marinade will tenderize them. Unfortunately that's only partly true. Acidity will break down the muscle fibers in the short term, but only on the very surface of the steak. If it's left in the marinade any longer, the acidity makes its proteins contract and toughen again. Enzyme-based tenderizers such as papain, and tropical fruits such as papayas that contain them, are more effective. Unfortunately they have to be used sparingly, otherwise they give the meat an unpleasantly mushy texture. Overall, physical tenderizing is usually a better option.
Let's Get Physical
There are two common methods for tenderizing a chuck steak physically. If you have a meat mallet -- available at most kitchenwares stores -- you can use that to break the bonds between the muscle fibers. Place your steak on a sturdy surface and pummel it gently but firmly with the rough side of the hammer, taking care to cover the entire surface on both sides. The steak will be larger and thinner when you're done. Alternatively, you can use a "jackard" tenderizer that uses a cluster of needles to puncture the steak and sever muscle strands. If you don't have one, ask your butcher to run it through his tenderizer. In either case, the steaks will be chewy but tender enough to enjoy.
Tender Chuck Cuts
Although the chuck is a tough cut, there are a couple of muscles within it that are tenderer and well-suited to grilling. One is the flatiron steak, a triangular cut that's usually grilled whole and then sliced like London broil. The chuck eye, Denver cut, shoulder tender and top blade are all relatively new and little-known cuts that isolate the tenderer muscles within the chuck. There are only a few pounds of these on any given steer, so most butchers won't cut them unless you ask. They vary in tenderness, with some giving a chewy but pleasant result, while others rival rib or loin cuts in tenderness.