McMillen moved to Australia in 1983 to lecture at
Monash University. She later move to the
University of Adelaide, where she was appointed the head of physiology from 1992. Her early research focused on the effects of prenatal nutrition on adult diseases. Her research was funded for two decades by the
Australian Research Council and the
National Health and Medical Research Council and she was on the
PMSEIC Working Group on
Aboriginal and Torres Strait Islander maternal and perinatal health. McMillen was also a Member of the Expert Advisory Group for Science in Australia Gender Equity (SAGE). McMillen has served on industry boards such as the Australia Automotive Industry Innovation Council, CRC for Advanced Automotive Technology and the CRC for Rail Innovation as well as the
South Australian Premier’s Climate Change Council and the NSW Innovation and Productivity Council. She has also served on the Boards of the Australian Business Higher Education Round Table, Universities Australia and the Universities Admissions Centre. McMillen was Deputy Vice-Chancellor and Vice President of Research and Innovation at the
University of South Australia from 2005 to 2011. In 2011, she was appointed as the seventh Vice-Chancellor and President of the
University of Newcastle. In November 2017, McMillen announced her intention to retire as vice-chancellor, just one year into her four-year contract renewal. She completed her term on 4 November 2018. At the end of her term, McMillen was presented with the Key to the City of Newcastle by
Nuatali Nelmes, the Lord Mayor of Newcastle, on 12 October 2018. Following her retirement from academia, McMillen became the fifth
Chief Scientist of South Australia on 18 October 2018. In the
2020 Queen's Birthday Honours, she was appointed an
Officer of the Order of Australia in recognition of her "distinguished service to medical science, and to tertiary education, to the community of South Australia, and to social equity." ==References==