Place the beef stew meat in the slow cooker. Add the diced onion, sliced carrots, and sliced celery on top.
Stir in the minced garlic, tomato paste, dried thyme, salt, and black pepper until the meat and vegetables are coated.
Pour in the beef broth and add the pearl barley. Drop in the bay leaves.
Cover and cook on low for 7 hours.
Stir in the drained kidney beans. Cover and cook for 1 more hour until the barley is tender and the beef is soft.
Remove the bay leaves before serving.