Fr. Gregg was born in Tarlac City on October 31, 1953. He studied at Holy Spirit College and Don Bosco Institute in Tarlac. After graduating from elementary, he entered the seminary of the Congregation of the Missions, popularly known as the Vincentians. His college years were spent at Adamson University where he graduated with a bachelor's degree in Philosophy. He continued his studies in Theology at UST finishing in 1979. In March of that year he was ordained a priest.

The first years of his priesthood were spent giving popular missions to some of the outlaying areas of Rizal, Bataan, Camarines Sur and Pangasinan. His work in the missions was interrupted when he was assigned for one and a half years as parish priest of St. Vincent de Paul Parish, Manila. After eight years conducting rural missions he was sent to the St. Vincent School of Theology in Quezon City to become the Director of Students and professor of pastoral theology. He taught in that major seminary for four years.

While working in the missions and teaching in the seminary, Fr. Gregg was also involved with an international non-governmental organization called the Movement for a Better World. He became the East Asian coordinator of this group for six years and facilitated training programs in Malaysia, Singapore, Thailand, Burma, Japan, and Korea.

In August of 1992, he was sent to the United States to continue his graduate studies. He started his master's degree in Organizational Development at Loyola University, Chicago, Illinois. While in Chicago, he worked in a parish and was consultant to the Ethnic Ministries of Archdiocese of Chicago.

In August of 1993, he joined the doctoral program in Organizational Behavior of the Weatherland School of Management at Case Western Reserve University, Cleveland. Ohio. During the six years that he studied in Cleveland, he worked at a parish and became the Spiritual Director of the Philippine American Community and Chaplain of University Hospitals.

He finished his doctoral degree in Organizational Behavior in January 2000. He is presently the President of Adamson University, Manila.