Brown the Beef: Heat olive oil in a large pot or Dutch oven over medium-high heat. Add the beef stew meat and cook, stirring occasionally, until browned on all sides, about 5-7 minutes. Remove the beef and set aside.

Sauté the Vegetables: In the same pot, add the onion, carrots, and celery. Cook for 5-7 minutes, until the vegetables begin to soften. Add the garlic and cook for an additional 1 minute.

Simmer the Soup: Return the browned beef to the pot. Add the dried thyme, dried rosemary, bay leaf, beef broth, and pearl barley. Stir to combine, and bring the soup to a boil.

Cook the Barley: Reduce the heat to low, cover the pot, and simmer for 45-60 minutes, or until the barley is tender and the beef is cooked through. Stir occasionally.

Add Peas (Optional): In the last 5 minutes of cooking, add the frozen peas (if using). Season the soup with salt and pepper to taste.

Serve: Remove the bay leaf before serving. Ladle the soup into bowls, garnish with fresh parsley, and enjoy!