In a large pot or Dutch oven, heat the olive oil over medium-high heat. Add the beef cubes, season with salt and pepper, and brown on all sides, about 5-7 minutes. Remove the beef and set aside.
In the same pot, add the chopped onion and garlic. Sauté for 2-3 minutes until the onion is translucent.
Add the carrots, celery, and mushrooms to the pot. Cook for another 5 minutes, stirring occasionally.
Return the browned beef to the pot. Pour in the beef broth and add the pearl barley, thyme, rosemary, and bay leaves. Stir to combine.
Bring the stew to a boil, then reduce the heat to low. Cover and simmer for about 1.5 to 2 hours, or until the beef is tender.
In the last 10 minutes of cooking, stir in the frozen peas. Remove the bay leaves before serving.
Serve hot, garnished with fresh parsley.