[1] Like a number of English Roman Catholics under the Penal laws who desired to enter religious life, he went to Douai in the County of Flanders, then the Spanish Netherlands.
[2] Mason rapidly became eminent in the Order, being created a Doctor of Divinity and appointed successively to the high administrative offices of Definitor, Guardian and Visitor to the Franciscan province of Brabant.
In that office, he visited Paris in an unsuccessful attempt to obtain permission for the settlement there of a colony of English Franciscan Sisters from their convent in Nieuwpoort in Flanders, where he had served as their confessor.
The latter include his Sacrarium privilegiorum quorundam Seraphico P. S. Francisco ... indultorum (Douai, 1636), a guide to the indulgences granted to members of the Franciscan Order.
He later wrote the Manuale Tertii Ordinis S. Francisci (Douai, 1643), a commentary and meditations on the Rule of the Third Order of St. Francis, in which he gives guidance to Franciscan tertiaries on their way of life.