Trim fat from meat. If necessary, cut roast to fit into a 3-1/2- or 4-quart slow cooker. Place meat in the cooker.
In a small bowl combine onion, port wine, tomato sauce, tapioca, Worcestershire sauce, thyme, oregano, and garlic. Pour over meat.
Cover and cook on low-heat setting for 8 to 10 hours or on high-heat setting for 4 to 5 hours. Transfer meat to a serving platter. Skim fat from gravy. Pass gravy with roast. If desired, serve with hot cooked pasta. Makes 8 to 10 servings.