Heat olive oil in a large Dutch oven over medium-high heat and brown the beef cubes on all sides, working in batches to avoid crowding, about 8 minutes total.
Remove beef and set aside, then add onion, carrots, and celery to the pot, cooking until softened, about 5 minutes.
Stir in garlic and tomato paste, cooking for 1 minute until fragrant.
Return beef to pot and add pearl barley, beef broth, water, bay leaves, thyme, salt, and pepper, bringing to a boil.
Reduce heat to low, cover, and simmer for 1.5 to 2 hours until beef is tender and barley is cooked through, stirring occasionally.
Remove bay leaves, adjust seasoning to taste, and garnish with fresh parsley before serving.