Prepare your ingredients by cutting the stew beef into 2-inch cubes and slicing the mushrooms.
Place the beef, mushrooms, onion soup mix, and black pepper into your slow cooker.
Pour the cream of mushroom soup and sherry over the beef mixture, ensuring everything is well-coated.
Cover the slow cooker and set it on low heat. Let the beef cook for about 8 hours.
Once cooked, serve the beef tips over a bed of warm, fluffy rice, making sure to spoon plenty of mushroom sauce on top.