A native of Cambridgeshire, de Fulbourn was translated to Tuam by a Papal bull dated 12 July 1286, having previously been Bishop of Waterford. He was succeeded at Waterford by his brother Walter de Fulburn, who was Lord Chancellor of Ireland 1283-1288. He served as Treasurer of Ireland from 1274–77 and Justiciar of Ireland from 1281-88.
The History of the Popes states that his appointment took place:
after a long contest between the rival claims of two other candidates, who had been severally elected by different portions of the Chapter of Tuam. Fulburn was an Englishman, and a member of the Order of Knights Hospitallers; he twice filled the office of Lord Justice of Ireland. He held the see of Enachdune as well as that of Tuam; but not without serious opposition from a rival, John de Ufford, who had been elected Bishop and had received the King's confirmation of his appointment.
According to Otway-Ruthven, his tenure as Justiciar was plagued by accusations of corruption and inefficiency. How much truth there was in the charges is difficult to say: the activities of Stephen and his brother Walter, who acted as his Deputy, prompted an official inquiry in 1284, during which numerous charges and grievances were aired, including debasing the coinage but he remained Justiciar until his death. He gave his name to the steeping, a debased form of the sterling silver penny. This was outlawed by Edward I.