[2] Born in Glasgow, McMillan worked as a sheet metal worker and took up speedway at the training school at Cowdenbeath in early 1966, following in the footsteps of two of his uncles who were also speedway riders - Doug Templeton and Willie Templeton.

[3][4] Later that year he broke into the Glasgow team in the British League and went on to average 3.54 points from thirteen matches.

McMillan rode in the British League Riders' Championship five times between 1969 and 1974, his best finish a third place in 1971.

[3] As well as riding in British speedway, McMillan rode in New Zealand, Poland, Norway, Sweden, Denmark, the United States, and Australia, where he finished as runner-up in the Queensland Championship in 1969/70.

[3] After retiring from the sport, McMillan worked as a machine examiner and a Technical Adviser to the Speedway Control Bureau.