Trim fat from meat. Cut steak into serving-size portions. In a 3-1/2- or 4-quart slow cooker place onion and mushrooms. Place beef on vegetables. In a bowl combine soup, wine, basil, marjoram, and pepper; 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. If desired, serve with hot cooked pasta. Makes 6 servings.