Add the lamb stew meat to the slow cooker.
Place the carrots, parsnips, turnip, potatoes, onion, and garlic on top of the meat.
Pour in the beef broth and add the pearl barley, rosemary, thyme, salt, and black pepper.
Stir everything together until the ingredients are evenly combined.
Cover and cook on low for 8 hours, until the lamb is fork-tender and the vegetables are soft.
Give the stew a final stir before serving.