Warm oil in a large saucepan over medium heat. Add onion and carrots and cook, stirring occasionally, until softened, about 8 minutes. Add mushrooms and sauté until they release their liquid, about 5 minutes. Add barley, oregano and thyme and stir 1 minute.
Add chicken broth and 3 cups water and bring to a boil. Lower heat, cover and simmer until barley is tender, about 30 minutes. Season with salt and pepper and serve.