Upon completion of school, he reported to Staging Battalion at Camp Pendleton, for further assignment to the 1st Military Police Battalion, 3rd Marine Division, Republic of Vietnam. Returning to the states, he was reassigned to the Infantry Training Regiment at Camp Pendleton.
Sergeant Major Overstreet subsequently completed successful tours on the Inspector-Instructor staff, Wichita, Kansas; recruiting duty in Des Moines, Iowa, and Detroit, Michigan; and returning to Marine Corps Recruit Depot San Diego, as a junior drill instructor, senior drill instructor, Series Gunnery Sergeant and Chief Instructor, Reassigned to Drill Instructor School, he was an Instructor, Drill Master, and Chief Instructor.
After completing First Sergeant School, he was assigned to Special Projects at Drill Instructor School, where he undertook the enormous task of completely transferring the Drill Manual onto video tape for a more optimal use during instructional periods. His promotion to first sergeant in February 1979 led to his second assignment on Okinawa as the First Sergeant, Headquarters and Service Co. 9th Engineer Support Battalion.
Upon his return from overseas, he was the First Sergeant of both Company B and C, 1st Battalion 4th Marines at Marine Corps Air Ground Combat Center, Twentynine Palms, California.
Promoted to his present rank in October 1983, Sergeant Major Overstreet became the Inspector Sergeant Major, MCAGCC, Twentynine Palms. Returning to Marine Corps Recruit Depot San Diego, he served as a Battalion and Regimental Sergeant Major in the Recruit Training Regiment. Transferring to Camp Lejeune, North Carolina, he served as the 6th Marines Sergeant Major. This assignment was followed by duty as Regimental Sergeant Major, 12th Marines, Okinawa.
On 6 April 1990, Sergeant Major Overstreet was posted as Depot Sergeant Major at San Diego. He was selected as the 12th Sergeant Major of the Marine Corps in April 1991, and assumed the post on 28 June 1991.
In February 2007, Sergeant Major Overstreet founded Veterans Direct Inc., a Texas (C) corporation and launched Veteran Caskets and Marine Caskets.