Pat beef dry with paper towels; generously season with salt and pepper.
Heat oil in large Dutch oven or soup pot over medium-high. Brown beef in uncrowded batches 3-4 minutes per side; transfer to plate.
In same pot, sauté onion, carrots, and celery 5-6 minutes until starting to soften; cook garlic another minute until fragrant.
Return beef and juices; add broth, barley, bay, and thyme.
Boil; reduce to low, cover, and simmer 75-90 minutes, stirring occasionally, until beef tender and barley cooked through.
Remove bay; taste and adjust salt and pepper.
Ladle into bowls; garnish with parsley and serve with crusty bread.