Heat olive oil in a large pot over medium-high heat. Add beef cubes and sear until browned on all sides. Remove and set aside.
In the same pot, add onion, carrots, celery, and garlic. Cook for 5–7 minutes until softened.
Return beef to the pot. Add beef broth, barley, diced tomatoes, bay leaf, thyme, salt, and pepper. Stir to combine.
Bring to a boil, then reduce heat to low. Cover and simmer for 1 to 1 ½ hours, stirring occasionally, until beef is tender and barley is cooked.
Remove bay leaf. Adjust seasonings if needed.
Serve hot, garnished with fresh parsley.