Heat the olive oil in a large Dutch oven over medium-high heat. Add the beef and cook until browned on all sides, about 5 minutes.
Add the onion, carrots, and celery. Cook for 4 minutes until the vegetables start to soften.
Stir in the garlic and tomato paste. Cook for 1 minute until the paste darkens slightly.
Pour in the beef broth. Add the pearl barley, thyme, bay leaves, salt, and pepper. Stir to combine.
Bring the mixture to a boil, then reduce heat to low. Cover and simmer for 45 minutes, stirring once or twice, until the beef and barley are tender.
Remove the bay leaves. Ladle into bowls and top with chopped parsley before serving.