A sirloin tip roast – also called a round or round tip roast – is a good choice for Crock-Pot cooking. Its location at the rear of the cow means a sirloin tip roast is a lean, weight-bearing muscle composed of tough muscle fibers and large amounts of connective tissue. Since the best way to relax muscle fibers, break down connective tissue and ensure your meat becomes tender is through moist heat and lengthy cooking times, a Crock-Pot is a logical and time-saving choice.
Trim visible fat from around the edges of the roast with a sharp kitchen knife. Although a sirloin tip roast is generally lean and you may find little fat to trim, removing even a small amount makes your meat healthier. Removing excess fat also makes the cooking liquid less fatty, especially important if you plan to thicken and serve the sauce with your meal.
Season the roast with a dry rub seasoning up to 24 hours before cooking it in your Crock-Pot. Keep it simple by rubbing the roast with a mixture of black pepper and minced garlic, or add extra flavor with additional seasonings such as coriander, paprika, fresh or dried rosemary, grated onion and dried thyme. Refrigerate the roast in a plastic food bag until 30 minutes before cooking.
Pour a small amount of slightly acidic liquid – about 1/2 cup - over the roast after adding it to your Crock-Pot. Acidic ingredients work to break protein bonds that hold muscle fibers together, as well as help dissolve connective tissue. A mixture of balsamic or apple cider vinegar, soy sauce, Worcestershire sauce and dry mustard provides a good base with which to start. As the meat cooks, juices that drain from the roast combine increase the quantity of liquid and give it a meaty flavor.
Cook the roast for eight to 10 hours on low or until a meat thermometer reaches 140 degrees F. Avoid overcooking, especially if you use acidic ingredients in your cooking liquid. Over time, acidic ingredients start to draw moisture out of your roast, and overcooking can cause it to become tough and dry.