Gregg has served three congregations in his 25 years of pastoral ministry: Wentworth Presbyterian Church in Wentworth, SD, while going to seminary; Cane Creek Baptist Church in Hillsborough, NC; and First Baptist Church in Rapid City, SD. Gregg also serves as a faculty mentor for students at Sioux Falls Seminary.
Gregg has served the ABC Dakotas Region under the leadership of Rev. Randy Rasmussen as a member of the Region Policy Board and as treasurer.
Gregg is married to Rev. Dr. Diane Lynn Janssen Hemmen who serves the Hermosa United Church of Christ, First Presbyterian Church in Rapid City, SD, and Rapid City Regional Hospital in the chaplaincy department. They have two children, Ainslee, a junior at Rapid City Central High School, and Eli, a freshman at Rapid City Central High School.