Since 1987 Marie has been a Member of the Victorian Parliament. She was a Minister in the Kennett Government; 1992 - 1996 as Minister for Health, and 1996 - 1999 as Minister for Conservation and Land Management. From 1987 to 1992 she was in the Shadow Cabinet with responsibilities for Conservation Forests and Land; Industry and Technology; Status of Women and Health.
Marie was involved in Policy formulation, and Budget preparation in the above areas, especially Health and Conservation, with overall management responsibility for the Victorian Health Department (Budget $1.3B) 1992 - 1996, and Department of Natural Resources and Environment ($100M) 1996 - 1999. She oversaw significant changes in the administration of health in Victoria, and introduced major restructuring of the natural resource management agencies and programs.
Coming to politics from a legal background, Marie entered State Parliament in 1987 and was appointed Shadow Minister for Conservation, Forests and Land. From 1990 - 1992 she was Shadow Minister for Health.