During the year 1993, Kay was the exchange senior minister at Toorak Uniting Church Archived 2012-03-17 at the Wayback Machine, in Melbourne, Australia.
William Sloane Coffin, senior pastor of the Riverside Church, New York City, Kay authored what became known as the ("augmented") Riverside baptismal formula: "In the name of the Father and of the Son and of the Holy Spirit, one God, Mother of us all," derived from the classical axiom that the ad extra works of the Persons of the Trinity are indivisible and based on Julian of Norwich's insight that Jesus Christ exercises the ministry of "Mother" towards the faithful.
He also oversaw the designing of Scheide Hall in conjunction with Ford, Farewell, Mills, and Gatch, Architects, and the selection of the Paul Fritts Organ donated by the American philanthropist, Joe R. Engle.
From 2002-2014, Kay directed the Joe R. Engle Institute of Preaching, securing for its work significant grants and endowments, and widening its outreach to Spanish-speaking pastors.
He has also lectured widely on the history, theology, and practice of Christian worship and preaching, as well as on homiletical theories--both those emerging from antiquity and from the post-Enlightenment era.