Sara Oust was born at the village of Vingelen in the parish of Tolga, Hedmark, Norway. She was the daughter of Embret (Engebret) Embretsson Oust and Mari Persdotter Røest Being fatherless at the age of seven, Sara Oust helped her mother carrying coal at the Røros Copper Works (Røros kopparverk).
She became the first female religious leader within the Haugean Ministry. She first became aware of the teachings of Hans Nielsen Hauge in 1799. She subsequently preached in Trøndelag between 1799 and 1805 alongside another female lay minister, Randi Hevle from Drivdalen in Sør-Trøndelag, and later Kirsti Fossen from Kvikne.
She reportedly had a beautiful singing voice and she also wrote psalms.
She first met Hans Nielsen Hauge in Oppdal during 1803. In 1805, Sara Oust married Ola Toresson Haugen (1776–1862) who was a farmer in Tolga.
However, following the death of Hans Nielsen Hauge in 1824, the Haugean movement became less supportive of lay ministers. Aarflot, Andreas (1979) Hans Nielsen Hauge, his life and message (Minneapolis: Augsburg Publishing) Furseth, Inger (2002) A Comparative Study of Social and Religious Movements in Norway, 1780s-1905 (New York City: Edwin Mellen Press) Pettersen, Wilhelm (2008) The Light In The Prison Window: The Life Story of Hans Nielsen Hauge (Kessinger Publishing, Limited Liability Company) Shaw, Joseph M. (1979) Pulpit Under the Sky: A Life of Hans Nielsen Hauge (Greenwood Press Reprint).
She successfully defended a collective of Haugeans from the local authorities, who gave up their attempts to implement the law after having seen she had too much support from the community.
