He was afterwards transferred to the geology department, and in December 1901 accompanied Professor F. T. Gregory on his expedition to Central Australia. In the preface to The Dead Heart of Australia Gregory paid a special tribute "To my assistant Mr Grayson on whom much of the hard work of the expedition fell".
He was later transferred to the geology department and participated in Professor F. T. Gregory's Central Australian expedition in December 1901. In the preface to The Dead Heart of Australia, Gregory acknowledged "To my assistant Mr Grayson, who undertook much of the challenging work on the expedition."