1 medium onion quartered 1 corned beef brisket (2 to 4 pounds) 3 carrots, sliced into 2-inch pieces 1 small turnip, sliced into 2-inch pieces 5 small potatoes, cut in half 1 cabbage,cored and quartered 1 Tablespoon, pickling spice place onions on the bottom Add the corned beef,place the pickling spice on top of meat and then top with carrots turnip and potatoes. Pour in enough water to completely cover the ingredients and meat, and then place the cabbage on top. Put the slow cooker on a low setting and cover. Cook until the beef is tender, about 8 to 10 hours. Plate corned beef atop of cabbage and vegetables, and serve warm.