Heat the olive oil in a large Dutch oven or soup pot over medium-high heat.
Season the beef with salt and black pepper.
Add the beef in batches and brown on all sides, about 5 to 6 minutes per batch. Remove and set aside.
In the same pot, add the onion, carrots, celery, and mushrooms.
Cook for 6 to 8 minutes until the vegetables begin to soften.
Stir in the garlic and cook for 30 seconds.
Add the tomato paste and cook for 1 minute.
Pour in the beef broth and diced tomatoes, scraping the bottom of the pot to loosen any browned bits.
Return the browned beef to the pot.
Add the pearl barley, bay leaves, thyme, Italian seasoning, and Worcestershire sauce.
Bring the soup to a boil.
Reduce the heat to low, cover, and simmer for 60 to 75 minutes, stirring occasionally, until the beef is fork-tender and the barley is cooked.
Taste and adjust the seasoning with additional salt and pepper if needed.
Remove the bay leaves before serving.
Garnish with chopped parsley and freshly cracked black pepper.