De Officio Regis reveals what Wyclif believed to be the place and duty of the king in the postlapsarian world, and explains some aspects of his thought that were under-developed in De Civili Dominio. The title De Officio Regis may lead one to expect Wyclif to give a more recognizably practical description of kingship in the treatise than he does, but it is no “mirror of princes.” Wyclif was firmly committed to uncovering the connection between the a priori truth of divine justice and its created instantiations, and has scant interest in the daily mechanics of royal administration. The work follows De Ecclesia in Thomson's chronological ordering of the tractates of the Summa Theologie, and was written in mid-1379.

The treatise is divided into twelve chapters, of which the first five explain Wyclif's belief that secular monarchs are ordained by God to reform and hold temporal iurisdictio over the church. In the first chapter, Wyclif begins with God's having ordained two vicars in His church: a king acting as vicar of God the Father with final authority in all temporal matters, and a priest acting as Christ's vicar with final authority in spiritual affairs. That the king's authority is over temporalia, while the priest's is over spiritual matters means that the sacerdotal dignity is of a higher nature and superior to royal dignity. But this elevated authority does not translate into a temporal authority beyond the king's; in every temporal affair, the king's authority is complete.