In France he continued his studies, receiving a scholarship at the Institut Catholique de Paris.
Then Riashi went back to Lebanon and taught for the next five years at the Basilian Saint John Seminary.
He was appointed principal of Saint Antoine Secondary School in Kfarshima, Lebanon for a year, before serving in the United States from 1970 until 1987.
He took over in 1978 pastoral work to Melkites in Detroit and was named Archimandrite on 21 July 1981 by Patriarch Maximos V Hakim.
In this office, Riashi was a participant in the Special Assembly of the Synod of Bishops (Catholic) on the Middle East.