In 1414 Oswald became a member of the entourage of Friedrich IV, Duke of Austria and Count of Tyrol, at the Council of Constance (1414–18); a portrait of Oswald can be found in the council's chronicle (by Ulrich von Richental). Oswald entered as a diplomat in the service of Sigismund, Holy Roman Emperor and King of Hungary. His first diplomatic voyage brought him to England, Scotland and Portugal, where he participated in the conquest of the Moorish city of Ceuta. In 1416 he joined King Sigismund in France and they traveled together back to Constance.