[2][3] Grey was posted to the 3rd Cavalry Regiment and, as a captain,[4] was deployed to Vietnam for which he was belatedly awarded the Commendation for Distinguished Service.
[8] He became Assistant Chief of Defence Force, Logistics and was made an Officer of the Order of Australia (AO) in 1991 for service in that role.
[9] He was appointed Chief of the General Staff in 1992[3] and made a Companion of the Order of Australia (AC) in 1995 for outstanding leadership, inspiration and dedication to the Australian Army during a period of profound restructuring.
[10] In retirement he established his own consultancy business based in Cairns; he also became a Non-Executive Director of Tarong Energy and Chancellor of James Cook University.
[3] In 2003 he was appointed Chairman of Queensland's Wet Tropics Management Authority Board.