Brown the Beef: In a large pot, heat olive oil over medium heat. Add the beef stew meat and brown on all sides. Remove from the pot and set aside.
Sauté Vegetables: In the same pot, add the onions, carrots, and celery. Sauté for about 5-7 minutes until the vegetables are tender. Add the garlic and cook for another minute.
Combine Ingredients: Return the beef to the pot. Add the barley, beef broth, diced tomatoes, Worcestershire sauce, thyme, bay leaf, salt, and pepper.
Simmer: Bring to a boil, then reduce heat to low. Cover and let simmer for about 1.5 to 2 hours, or until the beef is tender and the barley is cooked.
Finish and Serve: Remove the bay leaf. Taste and adjust seasoning if necessary. Serve hot, garnished with fresh parsley if desired.