Career
Mosteller is a Sister of Saint Joseph of Toronto. She first traveled from Ohio to board with the community and later entered the order after thriving under their supervision. She holds a degree in English from the University of Toronto and taught in schools in British Columbia and Ontario for 15 years.
She asked to be assigned to live and work with the community after hearing Vanier speak at the University of Saint Michael"s College and participating in a pilgrimage to Lourdes.
She described the way he spoke about people with disabilities as a "turning point in my life". In 1976 Mosteller became L"Arche Daybreak"s second Community Leader (Executive Director) and in 1985, she established Dayspring, a centre for spiritual growth, with Henri Nouwen.
She lived with the L"Arche Daybreak community for 40 years, leaving in 2011 to live with a small group of Sisters. She was the first person elected to hold the role of International Coordinator after Jean Vanier.
Holding the position for nine years, Mosteller traveled extensively, assisting with the birth of new L"Arche communities in multiple countries.
During her time in the position the L"Arche network expanded from 30 to 65 global communities. Nouwen credited her with being instrumental in fostering a maturity in his spirituality. As he states in his book The Return of the Prodigal Son, Mosteller "opened up the third phase of my spiritual journey.
She went on to oversee the founding of the Henri J.M. Archives and Research Collection at the John M. Kelly Library, University of Saint Michael"s College in Toronto.
Additionally, Mosteller lectures and gives retreats around the world. She currently lives in Toronto, Canada.
On November 5, 2011, Mosteller received an Honorary Doctorate from Tyndale University College and Seminary in Toronto in recognition of her "lifelong commitment to sharing the love of God with many of society"s marginalized people and her significant contributions to Christian life and learning over several decades".