Preheat large pot on medium-high heat and add butter and olive oil. Add onion, garlic, carrots, celery and saute for 5 minutes, stirring occasionally. Add Italian seasoning, salt, pepper and saute for another 30 seconds, stirring few times.
Refrigerate soup leftovers for up to 4 days. Pasta will keep absorbing the broth as it sits in it, so more likely you will have to add more chicken broth when reheating. Do not add water as it will dilute the flavor of orzo lemon chicken soup.