Mary Grant Bruce was born near Sale, Victoria, the fourth child of Irish and Welsh parents. Educated at Miss Estelle Beausir's Ladies High School, she matriculated in 1895 with honours in English, history and botany. After winning the Shakespeare Society's annual prize several times, she began work as a journalist, writing for the Age and the Leader and contributing articles and stories to a variety of magazines.
Bruce wrote many books, but she is best remembered for the Billabong series of children's books. The first in the series, A Little Bush Maid, was published in 1910. Fourteen more titles appeared during the next thirty-two years, attracting a huge audience for the wholesome Australian family potrayed in the series. Scholars have argued that Bruce's depiction of the bush in her popular series and other books had an enormous impact on the way white Australians viewed their relationship with the land. Bruce's other publications include a book of Aboriginal legends, a collection of radio talks and an enormous amount of uncollected prose and poetry in newspapers and magazines.
Bruce continued to write for magazines while she wrote her children's books and acted as editor of Woman's World during 1926. With her English husband, the writer George Bruce, and family, she moved between Australia and Europe several times, once contemplating permanent residence in Ireland until a son was killed in a shooting accident. The family returned to Australia in 1939. Bruce's husband died ten years later. Then, while visiting England in 1954, Mary Grant Bruce decided to stay. She died in Sussex, England, in 1958.