Maurice de la Taille's Mysterium Fidei (1921) was, as one of its reviewers remarked, a veritable ‘theological event’, both in terms of its methodology and its overturning of post-Tridentine theology on eucharistic sacrifice. De la Taille's work has been long overlooked in the history of theology in the early twentieth century. The paper demonstrates that de la Taille's work on the Eucharist proves an early example of nouvelle théologie and a catalyst for the the liturgical movement. Conciliar and pre-Conciliar documents presuppose his Mysterium Fidei. Through the retrieval of a patristic and medieval teaching about sacrificial oblation, de la Taille disperses the web of immolationist theories about the sacrifice of the Mass that had dominated baroque and early modern theology.