Place the beef stew meat in the bottom of the crockpot.
Add the pearl barley, sliced carrots, diced celery, diced onion, and frozen green beans on top of the beef.
Pour the beef broth over the ingredients.
Sprinkle in the dried thyme, add the bay leaves, and season with salt and pepper.
Stir gently to combine everything, then cover the crockpot.
Cook on low for 8 hours until the beef is tender and the barley is cooked through.
Remove the bay leaves before serving.