For 1907–1929, Brian G. McIntosh, (''The Scottish Mission in Kenya, 1891–1923'' ), PhD thesis, University of Edinburgh, June 1969, p. 208, n. 29.〕
Stevenson worked at first for the church's Kikuyu mission at Thogoto, then from 1912 for its mission at Tumutumu in Karatina, set up by Rev. Henry Scott and Dr. John Arthur in 1908.〔For 1912, McIntosh 1969], p. 241, n. 120.〕〔 She established and ran a girls' school, which became Tumutumu Girls' High School, taught sewing, knitting and hygiene, worked in the hospital, trained teachers and helped to translate the Bible.〔("Letter from Marion S Stevenson" ), University of St Andrews archives.

For Thogoto, Johnson Kiriaku Kinyua, ''The Agikuyu, the Bible and Colonial Constructs: Towards an Ordinary African Readers' Hermeneutics'', University of Birmingham (PhD thesis), p. (10 ).〕〔Robert Benedetto, Donald K. McKim, ''Historical Dictionary of the Reformed Churches'', Lanham: Scarecrow Press, 2009, p. (464 ).〕
According to theologian James Karanja, citing a Church of Scotland memorandum, in 1929 Stevenson coined the term "sexual mutilation of women" to describe female circumcision, a practice of great importance to the Kikuyu people, Kenya's largest tribe. The Kenya Missionary Council followed suit, and began referring to it that year as sexual mutilation, rather than as circumcision or initiation. It is now widely known as female genital mutilation.〔James Karanja, ''The Missionary Movement in Colonial Kenya: The Foundation of Africa Inland Church'', Göttingen: Cuvillier Verlag, 2009, p. (93 ), n. 631.