He was born and raised in Hartley in the Blue Mountains, about 50 kilometres (31 mi) north-west of Sydney and later moved to the McPherson Range near Beaudesert in South East Queensland, Australia.

[2] O'Reilly is best known for the discovery of the 1937 crash site in Lamington National Park of a Stinson Model A airplane, the VH-UHH Brisbane, and the organization of rescue crews that retrieved two survivors.

[3][4] Using his bushcraft and geographical knowledge, as well as inferring from the plane's filed flight plan, O'Reilly found the crash site.

At the ceremony he paid tribute to the two survivors and one of the five victims, Jim Westray, who died from exposure after breaking his ankle and crawling several miles while trying to get help for the others.

The Australian philosopher David Stove has written a short appreciation of O'Reilly's life and books.