Pat beef cubes dry and season with salt and pepper. Heat olive oil in a large Dutch oven over medium-high heat. Sear beef in batches until deeply browned on all sides. Transfer to a plate.

Reduce heat to medium. Add onion, carrots, and celery to the pot and cook for 5-7 minutes until softened. Stir in the minced garlic and cook for 1 more minute until fragrant.

Pour in the beef broth, scraping up any browned bits from the bottom of the pot. Return the beef and any juices to the pot. Add diced tomatoes, Worcestershire sauce, thyme sprigs, and the bay leaf.

Bring to a boil, then reduce heat to low, cover, and simmer for 1.5 hours, or until the beef is becoming tender.

Stir in the rinsed pearl barley. Return to a simmer, cover, and continue to cook for 45-60 minutes, until barley is tender and the beef is fall-apart soft.

Remove thyme sprigs and the bay leaf. Taste the soup and season with additional salt and pepper as needed. Garnish with fresh parsley before serving.