In a large pot, heat a tablespoon of oil over medium-high heat.
Add the cubed beef to the pot and brown on all sides, about 5-7 minutes.
Remove the browned beef and set aside. In the same pot, add onion, carrots, celery, and garlic. Sauté until softened, about 5 minutes.
Return the beef to the pot and stir in the pearl barley, thyme, bay leaf, and beef broth.
Bring the soup to a boil, then reduce the heat to low and cover, letting it simmer for 1.5 to 2 hours.
Once the beef is tender and the barley is cooked, season the soup with salt and pepper to taste, and remove the bay leaf before serving.