In 1894, Cowan was one of the founders of the Karrakatta Club, the first women's social club in Australia. She became prominent in the women's suffrage movement, which saw women in Western Australia granted the right to vote in 1899. Cowan was also a leading advocate for public education and the rights of children (particularly those born to single mothers). She was one of the first women to serve on a local board of education, and in 1906 helped to found the Children's Protection Society, whose lobbying resulted in the creation of the Children's Court the following year. Cowan was a co-founder of the Women's Service Guild in 1909, and in 1911 helped establish a state branch of the National Council of Women.