If you want fajitas in an hour -- don't reach for a fresh cut of brisket. However, if you've got plenty of time or a handy stash of leftover brisket in the refrigerator, then you can use brisket for fajitas. Brisket is full of collagen and muscle, which can make the meat tough and chewy. But if you cook brisket long enough, the meat softens, making it easier to roll up in tortillas and enjoy.

Most store-bought brisket has had both a layer of fat and the breast bone removed. This type of brisket cooks best braised or stewed in liquid. Otherwise, the meat will become dry and tough, making your fajita chewy and difficult to swallow. Packer-trimmed brisket still has a thick layer of fat around the meat. These cuts work best cooked for a long period on the barbecue or in a smoker set to low temperatures. The fat helps keep the meat moist. Whether braised or smoked, brisket can take as long as six hours to cook.

If you recently cooked a brisket, fajitas give you a good way to use up the extra meat. Any leftover brisket must be stored in a refrigerator set between 35 and 40 degrees Fahrenheit, and it will remain safe to eat for three to four days. If the meat has been left out in the open for two hours -- or one hour in temperatures over 90 degrees F -- it's not safe to eat. When reheating the brisket for fajitas, make sure the meat reaches 165 degrees F, advises the Food Safety website.

Using smoked brisket in a fajita puts a Tex-Mex spin on a classic Mexican dish. Instead of rolling the meat in fajita mix or chili powder, try using a barbecue rub. Or smoke the brisket over mesquite chips or hickory to create a classic smoked meat flavor. The smoky taste works well alongside the usual fajita ingredients of refried beans, salsa and guacamole.

If you're barbecuing the brisket instead of using an all-purpose rub, use fajita mix or seasoning on the meat. Work it into the brisket a few hours before cooking so the flavor gets deep into the cut. If the brisket is already cooked, try marinading slices in a mix of lime, olive oil garlic, oregano, cumin and cilantro overnight. Season with a little salt and pepper before frying up with chopped jalapenos, onions and tomatoes for your fajita feast.