He became a law clerk for Lilley & O'Sullivan before being employed by Samuel Griffith as an assistant.

[1] In 1899 Macregor married Mabel Newton and together had two sons and two daughters.

[4] Macgregor died in 1936[1] and his funeral proceeded from his New Farm residence, "Craigroyston", to the Mt Thompson Crematorium.

[5][6][7] Representing the Nationalist Party, he won the seat of Merthyr in the Queensland Legislative Assembly in 1920, defeating the sitting member, Peter McLachlan of the Labor Party.

[1] MacGregor was the editor of the State Reporter and Law Journal, a member of the Queensland Club, and president of the Women's College Council from 1914-1936.