In a large pot over medium heat, add olive oil. Once oil is shimmering, add diced onion, celery, and carrots. Cook until veggies are crisp-tender, stirring occasionally, for about 7–9 minutes (reduce heat if veggies are browning too quickly). Add minced garlic and stir for 30 seconds.
Add the seasonings and stir for 30 seconds. Pour in the chicken broth and add the bay leaf if using. Increase heat and bring to a boil. Once boiling, add the orzo. Cook according to package directions, subtracting 2 minutes from the recommended cooking time.
Stir in the shredded rotisserie chicken and the spinach. Gently stir to warm through the chicken and allow the spinach to wilt, about 1–3 minutes. Remove from heat. Stir in 1-1/2 teaspoon lemon zest and 3–4 tablespoons lemon juice. Season to taste if any additional salt or pepper is needed.
Ladle the soup into bowls and garnish, if desired, with fresh thyme. Add optional Parmesan cheese to individual bowls. Serve with crusty bread.
Notes
Note 1: Grab a pre-chopped mirepoix blend from the store’s produce aisle or process the veggies in a food processor for a quick dice. You’ll need about 1/2 a large onion, 3–4 stalks of celery, and 3 carrots.Note 2: Keep in mind that since you cook the orzo in this soup, it will continue to absorb the liquid. This soup is best eaten the same day it’s made.Note 3:If available, choose a lemon herb seasoned rotisserie chicken for extra lemon and herb flavor.Note 4: Add lemon juice and zest gradually according to your taste preferences. If you’re a big lemon fan, consider using lemon herb seasoning (e.g., Mrs. Dash) or lemon pepper instead of regular pepper in the soup.Note 5: Serving suggestions: fresh thyme, Parmesan cheese, and crusty bread.Storage: Store the soup 2–3 days in the fridge, but note that the orzo may absorb some liquid, so adjust with more chicken stock when reheating for desired consistency. Avoid freezing; add the orzo after thawing and reheating for best texture.