The Cut

• Reheating beef can make it tough, depending on the cut. Tough cuts of beef such as chuck, brisket and top and bottom round actually need long, slow cooking to an internal temperature around 185 degrees Fahrenheit. At this temperature, the connective tissue in the meat melts into gelatin, tenderizing the meat and giving it flavor. You're not likely to toughen one of these roasts, unless you reheat it on high heat. Very tender cuts of beef, such as prime rib and tenderloin need only quick cooking to an internal temperature of between 125 and 135 F, which is lower than the U.S. Department of Agriculture's recommended minimum temperature of 145 F. If cooked longer, they may toughen, which is why it's important to reheat them gently and quickly. They may become tough if you cook them so their internal temperature rises above 135 F.

The Method

• The safest way to heat large portions of meat is in the oven. Place the meat in a baking dish and cover it with foil. Heat it at 350 F, just until it's warmed through. Heating it for longer periods, or at higher heat can dry it out and toughen it. Heat individual pieces of meat in the microwave, just for a minute or two. Watch the meat closely and don't overcook it.

The Secret's in the Sauce

• Adding a liquid or sauce to the meat can help prevent dryness and toughening. Pour a bit of broth or red wine in the pan before you reheat meat in the oven. If the meat was served with gravy, add the gravy to the heating container. Ground beef casseroles that contain sauces -- such as sloppy joes or tamale pies -- are less likely to become toughened because the liquid in the dish helps maintain moisture.

Smart Solutions

• If, in spite of your best efforts, the beef still seems tough after reheating, your best option is to cut it into smaller pieces. Slice the meat thinly across the grain for sandwiches, fajitas or stir-fry. To find the grain, look for the lines running through the meat or observe how the meat fibers naturally lie. Cut perpendicular to these lines and you'll shorten the meat fibers, which tenderizes the meat. Shredding the meat also disguises any toughness. Top shredded beef with barbecue sauce for an instant meal.