Place the beef stew meat and pearl barley into the slow cooker.
Pour in the beef broth and add the can of diced tomatoes with their juices.
Add the frozen carrots, frozen peas, dried thyme, and garlic powder.
Season with salt and pepper, then stir everything together.
Cover and cook on low for 7 to 8 hours until the beef is tender and the barley is cooked through.
Stir once more before serving.