Place beef pieces into a large ziptop bag. Add flour, salt and pepper. Shake to coat evenly.
Heat olive oil in a large skillet or pot over medium heat. Brown coated beef pieces on both sides until browned, about 5 minutes per side. Transfer beef to 5 quart crock pot on high.
In same skillet beef was browned, add 2 more additional tablespoons of olive oil. Saute carrots, celery, onions, mushrooms, zucchini, garlic and thyme. Cook and stir for about 10 minutes. Transfer to crock pot. Stir in beef broth, barley, salt, pepper and worcestershire sauce. Close with lid and cook on high for 3-4 hours. About an hour before soup is done, stir in fresh parsley. Serve with crusty bread.