Store any leftover orzo soup in an airtight container for up to 4 days in the refrigerator, or freeze for up to 3 months. One quick word about storing orzo soup. As with any pasta, the orzo will keep soaking up the chicken stock as it sits. So, if it sits in the fridge for a day or two, you will find that your leftovers have a consistency closer to risotto, rather than soup.  To bring things back to a soup consistency, just add a little more broth when you reheat.