After he returned to England and married Elizabeth Clare on 11 August 1886, the couple soon migrated to Victoria (Australia) where Grayson worked as a nursery gardener.
Becoming interested in science he joined the Field Naturalists Club of Victoria, studied botany and did some work on the diatoms, a group of minute plants.
In 1897 some beautiful work Grayson had done in cutting sections of plants led to his being given a position in the physiology department of the University of Melbourne under Professor C. J. Martin.
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".
[2] In 1910 Grayson was associated with Daniel James Mahony in the preparation of a paper on "The Geology of the Camperdown and Mount Elephant Districts",[3] and in the same year, while working at the university under Professor E. W. Skeats, who succeeded Gregory, Grayson made a highly efficient apparatus for preparing rock sections, a description of which will be found in the Proceedings of the Royal Society of Victoria for the year 1911.