Back in Melbourne in 1901 after extensive overseas studies, Portia held an exhibition in her Collins Street studio. Portraits became her specialty and she later painted Edith Cowan which hangs in Parliament House, Perth, and (Sir) John Quick which was accepted and hung in the National Library, Canberra. She also painted murals and was a member of the Victorian Artists' Society. Around 1904 her family moved to Sydney, where in 1914 she exhibited mainly oils and watercolours of the shores of Sydney Harbour and Victorian rural scenes, with some portraits.

In the Sydney Morning Herald and over the radio she frequently expressed her views on such subjects as buying Empire goods, the use of preservatives in foodstuffs, the date-stamping of eggs, the marking of lamb and the high price of milk and bread. Active on the committee of the National Council of Women of New South Wales, Geach was a delegate to the International Council of Women's conference in Washington in 1925. She believed in equal pay for men and women and the right of women to hold public office. In 1926, while overseas, she exhibited at the salon of the Société Nationale des Beaux-Arts, Paris.

In 1941 of Portia was expelled from the Housewives Progressive Association after years of rivalry with its paid chairwoman of directors Eleanor Glencross. Geach also alleged that the association had been working in cooperation with the Meadow-Lea Margarine Co. Pty Ltd. In 1947 she formed the breakaway Progressive Housewives' Association and was president until 1957. She also served on the council of the Australian Women's Movement against Socialisation from 1947, and belonged to the Women's Club, Sydney, and the Lyceum Club, Melbourne.

Geach's sister Kate provided in her estate for an annual £1,000 prize, known as the Portia Geach Memorial Art Award, for a portrait by a woman artist (for a complete list of winners, see http://www.trust.com.au/Content.aspx?topicID=71).

Sources used to compile this entry: Wright, Andree, 'Geach, Portia Swanston (1873 - 1959)', in Australian Dictionary of Biography Online, Australian National University, 2006, http://www.adb.online.anu.edu.au/biogs/A080650b.htm.