Fr. Griego took up his first assignment as a priest with the Society of St. Pius X in Manila, Philippines, in 1995.
After a year there, he was assigned as prior of Durban, South Africa, where he remained for two years, before being re-assigned to Manila, this time as prior. His second stay at Manila was for five years.
Afterwards, he took up the post as headmaster of St. Mary's Academy and College in Saint Marys, Kansas. That assignment also lasted five years, from 2003-2008.
Next came his assignment as Rector of Holy Cross Seminary in Australia, a post that Fr. Griego held for seven years.
In August of 2015 Father arrived to his nomination as superior of the autonomous house of the SSPX in Dublin, Ireland. By taking up residence in Europe, Father has served as a priest of the SSPX in five continents - Asia, Africa, North America, Australia, and Europe!