This chapter provides a rare insight into everyday life in an early modern overseas collegial institution. It focuses on the purpose and daily operations of the English Jesuit college of St Omers, founded in 1593, now located at Stonyhurst in Lancashire, England.Through surviving documentation, including the extraordinary ‘Custom Book of St Omers’ penned by the college’s third rector, Gilles Schondonck, it explores how the rule book structured the lives of collegians and expressed the primary function of the institution. Specifically, it places the Customs Book in the context of the St Omers’ sodality, whose declared mission was the reconversion of England to Catholicism. The Customs Book emerges as a contemporary testament of spiritual and cultural identity tailored for an early modern educational institution dating from 1599 to c. 1650. It is one of the earliest surviving responses to the comprehensive Jesuit system of education, the Ratio Studiorum, published in January 1599. Elements of the Customs Book have, before now, appeared in the work of Hubert Chadwick, Joseph McCabe, and Maurice Whitehead but it has not yet been examined as a complete document. This paper seeks to assess the manuscript in the light of its significance as a manual of operations for English Jesuit collegiate education and for the spiritual and cultural formation of a community in exile.