In a large pot or Dutch oven, heat olive oil over medium-high heat. Carefully add the beef cubes and brown them on all sides, ensuring they develop a rich, flavorful crust.

Add the chopped onion, carrots, and celery to the pot and cook, stirring occasionally, until they begin to soften, approximately 5-7 minutes. This step is crucial for building flavor in the base of the soup.

Stir in the minced garlic, rinsed pearl barley, beef broth, diced tomatoes (undrained for extra flavor), dried thyme, dried rosemary, salt, and black pepper. Ensure all ingredients are well combined.

Bring the mixture to a boil, then reduce the heat to low, cover the pot, and let it simmer for at least 1.5-2 hours, or until the beef is incredibly tender and the barley is fully cooked through and has reached a delightful, chewy consistency. Stir the soup occasionally to prevent sticking and ensure even cooking.

Taste the soup and adjust the seasoning as needed, adding more salt, pepper, or herbs to your preference. Garnish with freshly chopped parsley before serving, adding a touch of freshness and visual appeal.