Season the Oxtail generously with salt and pepper.
Heat Olive Oil in a large pot or Dutch oven over medium-high heat. Brown the Oxtail in batches, ensuring not to overcrowd the pot. Set aside.
Add Onion, Carrots, and Celery to the pot and cook until softened, about 5-7 minutes. Add Garlic and cook for another minute.
Return the Oxtail to the pot. Pour in Beef Broth, add Thyme and Rosemary. Bring to a boil, then reduce heat to low, cover, and simmer for 3-4 hours, or until the Oxtail is very tender.
Add Pearl Barley to the soup and continue to simmer for another 30-45 minutes, or until the barley is tender.
Season with additional Salt and Pepper to taste. Serve hot.
