Stirling read for the bar and was admitted at the Inner Temple in 1872, but never practised. Stirling returned to South Australia soon afterwards, became a pastoralist, and bred prize horses and merinosheep. He entered the South Australian Legislative Assembly in 1881 for Mount Barker, which he held until April 1887, and afterwards represented Gumeracha until 1890, when he became a member of the then-conservative South Australian Legislative Council, representing the Southern District. In December 1899 Stirling was chief secretary in the conservativeSolomon government but this ministry was defeated as soon as the house met. In 1901 Stirling was elected President of the South Australian Legislative Council, and would serve in the position for a record 31 years. Stirling was made a knight bachelor on 14 August 1902, after the honour had been announced in the 1902 Coronation Honours list published on 26 June 1902. He was appointed a Knight Commander of the Order of St Michael and St George in 1909 and Officer of the Order of the British Empire in 1918. He continued his interest in sport all his life, pioneering polo in South Australia and captaining the team which twice beat Victoria. For a time Stirling was master of the Adelaide Hounds and was a well-known figure at racing meetings. He was a member of the Royal Agricultural and Horticultural Society and its president from 1891 to 1893; he was president of the Society for the Prevention of Cruelty to Animals, the Pastoralists' Association, the St Peter's Old Collegians Association, the South Australian Zoological and Acclimatization Society, and was a member of the Adelaide University council. He was a member of the Caledonian Society of South Australia, and its Chief 1885–1886. Stirling also possessed a good business sense and was a director of well-known companies. In politics he was respected as a man of individuality but not regarded as a first-rate speaker. Stirling found his ideal position as president of the council, admirably carrying out his duties; as the years passed becoming a kind of elder brother to the newer members.
Family
On 2 December 1882, Stirling married Florence Marion, daughter of Sir William Milne and was survived by his wife, three sons and two daughters. His elder daughter Madge Mary Stirling married Knox Lister Colley on 28 January 1914. Knox was a son of R. B. Colley, first mayor of Glenelg.