Place the beef stew meat, pearl barley, carrots, celery, onion, beef broth, diced tomatoes, garlic, thyme, salt, and pepper into the slow cooker.
Stir the ingredients until they are evenly combined.
Cover the slow cooker and cook on low for 8 hours or on high for 4 hours, until the beef is fork-tender and the barley has softened.
Ladle the soup into bowls and top each serving with a sprinkle of fresh parsley.
Notes
If the soup thickens too much after cooking, stir in a splash of extra broth before serving. Leftovers keep well in the fridge for three days and reheat gently on the stovetop without losing much texture. Skip the parsley if you prefer a simpler finish.Course: Soup
Cuisine: American
Equipment: Slow Cooker, Knife, Cutting Board