O'Connor Desmarais & Co. is an accounting firm in McLean. O'Connor Desmarais & Co. specializes in bookkeeping, financial advising and accounting services for small- to mid-sized businesses. However, during tax season,it also provides tax preparation services fromthe same offices. The founders, Carl F. Desmaris, C.P.A. and Terry O'Connor, C.P.A., have decades of combined experience.