George S. Brock qualified as Bachelor of Medicine and Master in Surgery at the University of Edinburgh in 1879 and that same year published a paper on a two-headed sartorius muscle in the Journal of Anatomy and Physiology. He was licensed as a medical practitioner in the Cape Colony in August 1883, practised at Herschel in 1884, but after a few years moved to the South African Republic (Transvaal), where he was admitted as a medical practitioner in 1888. In 1892 he qualified as Doctor of Medicine (MD) at the University of Edinburgh with a thesis entitled On the bilharzia haematobia, for which he was awarded a gold medal. After his return to South Africa in 1892 he read a paper on his thesis topic before the Transvaal Medical Society. The paper was not published, as it formed part of his thesis. He subsequently published two papers on bilharzia in The Lancet (1893) and the Journal of Pathology and Bacteriology (1894). He settled in Rustenburg on his return, and practised there until at least 1897.
Brock is credited with the earliest record of animal poisoning due to "gifblaar" (Dichapetalum cymosum). In 1890 he sent specimens of the plant from the vicinity of Pretoria to P. MacOwan*, Colonial Botanist of the Cape Colony.
By 1907, and still in 1915, he resided in Rome, Italy. He was elected a Fellow of the Royal Society of Edinburgh in 1893.