 Mason-Cox operated an optometry business in the rural city of Queanbeyan, New South Wales.He later served at senior levels in the Australian Public Service and served as secretary and senior adviser to a number of federal Parliamentary committees including the Defence Sub-Committee and the Family Law Committee inquiry into the Child Support Scheme.Mason-Cox was also Corporate Counsel to Elders IXL Ltd in Adelaide and trained as a solicitor at Freehills in Sydney.