William Grice Mason qualified as Bachelor of Science (BSc, presumably in agriculture) in Edinburgh and was elected a Fellow of the Highland and Agricultural Society of Scotland (FHAS). On 1 September 1898 he was appointed as the first principal of the Agricultural School at Elsenburg (later the Elsenburg College of Agriculture) near Stellenbosch. This institution, formerly the Stellenbosch School of Agriculture and Viticulture, directed by F. Blersch* and functioning under the auspices of Victoria College, moved to the farm Elsenburg in August 1898. From this time it functioned as an autonomous educational institution under the Department of Agriculture of the Cape Colony. The staff gradually increased, courses were improved, and it became a centre for research and progressive farming practices in the winter rainfall region.
During the first year or two Mason spent most of his time developing the farm. The property was re-surveyed and then fenced, buildings were improved or erected, a new road was constructed linking the farm to Mulder's Vlei station, thousands of fruit trees and vines were planted out, and various crops sown. Testing out various imported varieties of oats for rust resistance, comparing the effects of different fertilisers, and comparing various fodder plants and grasses were initiated in 1900. Further tests on the effects of fertilisers on wheat and oats were carried out on other farms in the Western Cape the next year, while many varieties of wheat were compared at Elsenburg.
Mason was a member of the South African Philosophical Society from 1899. He also joined the South African Association for the Advancement of Science soon after its formation and served on the committee of Section C (which included agriculture) in 1902/3. During the first half of 1903 he retired from his post, intending to pay a brief visit to England and then settle in Bechuanaland (which included parts of the present Northern Cape and North West Province, as well as Botswana). However, he died that same year. Just before his death he wrote a Report of Mr W. Mason, ex-principal, Elsenburg, on the working of the Agricultural college at Elsenburg, during his tenure of office as principal (Cape Town, 1904) in which he made various recommendations relating to the required background of students and the nature of their agricultural training. His successor, Frank P. Walker, remarked in his annual report for 1903 that "when the history of agricultural education... in South Africa is written the name of Mr Mason will receive more than honourable mention".