Pairing a roast beef with instant onion soup mix and canned soup is a tasty way to prepare any type of roast but is an especially effective cooking technique to moisten and tenderize an inexpensive roast. Preparing the roast takes only minutes. Put the roast in your oven on low temperature before you leave for work in the morning, or cook the meat at a higher temperature for a roast that will be ready in three or four hours, depending on the size.
Preheat your oven to 250 F if you want to slow-cook your roast beef all day. For a faster roast, preheat your oven to 325 to 350 degrees.
Line a large baking dish or Dutch oven with heavy-duty aluminum foil. Use enough foil to fold loosely over the roast.
Open a can of cream of mushroom soup. Use regular cream of mushroom soup, or substitute golden mushroom soup or garlic mushroom soup. Place the soup in a mixing bowl; then stir in onion soup mix.
Place the roast beef in the center of the baking pan. Spoon the soup mixture over the beef.
Bring the sides of the aluminum foil up over the beef. Join the ends and seal the aluminum foil securely, making a loose but airtight tent over the beef.
Place the roast beef in the preheated oven. Roast the beef for 8 to 10 hours at 250 degrees or 3 to 4 hours at 325 to 350 degrees. Use a meat thermometer to test your meat. For a medium rare roast, cook the meat until it reaches an internal temperature of 135 degrees. For a medium roast, cook the meat until it reaches an internal temperature of 150 degrees.
Remove the roast beef from the oven and allow the meat to stand for about 15 minutes. The meat will continue cooking during standing time; the temperature will rise by 5 to 10 degrees. Allowing the meat to stand also results in meat that is easier to slice.
Remove the roast from the baking pan and place it on a cutting board. Slice the meat and serve.