When the Wran government achieved power in May 1976 (ending the Labor Party's 11-year period in opposition), Mulock became Minister of Justice (until October 1978) and Minister for Services (until February 1977). He was also Minister for Housing from February 1977 to October 1978, Minister for Mineral Resources and Development from October 1978 to February 1980 and Minister for Mineral Resources and Technology from February 1980 to October 1981. Mulock served as Minister for Education from October 1981 to February 1984.