In a large pot or Dutch oven, heat the olive oil over medium-high heat. Add the beef and brown it on all sides, about 5-7 minutes. Remove the beef from the pot and set it aside.
In the same pot, add the onion, garlic, carrots, and celery. Sauté until softened, about 5-7 minutes.
Return the beef to the pot and add the barley, broth, thyme, and bay leaf. Bring the soup to a boil, then reduce the heat to low and let simmer for 1 hour or until the beef is tender and the barley is cooked.
Remove the bay leaf from the pot, and season with salt and pepper to taste.
Ladle the soup into bowls and sprinkle with chopped parsley (if desired) before serving. Enjoy!