Heat the olive oil in a large Dutch oven or large pot.
Add the carrot, onion, celery, garlic, thyme, bay leaf, lemon zest and salt. Saute ingredients over medium heat until vegetables begin to soften.
Add the chicken stock and lemon juice. Bring to a boil.
Add the chicken and orzo. Simmer until orzo is cooked through. (see Note not serving soup right away)
Just before serving add parsley and remove bay leaf. Garnish with salt and black pepper if needed and Romano cheese if desired.
Notes
If you're serving right away you can add the orzo pasta and chicken at the same time until the orzo is cooked. If you plan on serving later it at a later time you may want to cook the orzo separately and add right before serving. The orzo pasta tends to soak up all the liquid and can become quite thick if you simmer the soup for a long time. You can always add more chicken stock if you want to thin it out a little.Source: slightly adapted from Food.com