Griswold is a member of the Joint Standing Committee of the Primates of the Anglican Communion and the Anglican Consultative Council. He was co-chair of the Anglican-Roman Catholic International Commission from 1998 to 2003. He was a member of the standing committee for the 1998 Lambeth Conference. He has also served on diocesan, national and international committees for liturgy, worship and ecumenism. He is also a member of The Fellowship of Saint John.