Heat the olive oil in a large pot over medium heat. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks.
Stir in the onion, carrots, and mushrooms. Cook for 5 minutes until the vegetables begin to soften.
Add the garlic and cook for 1 minute until fragrant.
Mix in the tomato paste, thyme, salt, and pepper. Stir to coat the meat and vegetables evenly.
Pour in the beef broth and add the pearl barley. Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 40 minutes until the barley is tender.
Stir in the fresh parsley just before serving.