He was probably of Danish ancestry. He was related to Oswald, Bishop of Worcester and later Archbishop of York, and Thurcytel, who was abbot of Bedford Abbey. All three men were landowners in the eastern midlands, with Oskytel owning lands at Beeby, in Leicestershire. No other information about Oskytel's birth and upbringing is known. A legend stated that his father was a Dane who arrived in England as part of a pagan war band.
He was selected to the see of Donchester sometime between 934 and 951, probably pretty close to 951 for the Anglo Saxon Chronicle says that he had been a bishop for twenty-two years when he died. 951 is also when he first attests a charter as bishop. A previous mention of an "Oscetel" as either a sacrist or treasurer in 949 may or may not be the same person. Oskytel only starts showing up consistently after the death of King Edred of England, who left the bishop some bequests in his will. At first Oskytel supported King Edwy of England, but in about 958 he switched to supporting Edwy's brother King Edgar of England.
He became archbishop in 958. However, he continued to hold the see of Dorchester along with York, a practice known as pluralism. It is probably due to Oskytel's pluralism that Nottinghamshire was added to the see of York instead of remaining with Dorchester where it had been before. The Anglo Saxon Chronicle from Ramsey says that he went to Rome for his pallium, but no other sources say that he did so. While archbishop he advanced the career of his kinsman Oswaldv by bringing Oswald to the attention of Dunstan, and encouraging Oswald's foundation of Ramsey Abbey. Oskytel also was a benefactor to the new monastic houses that were formed in the fens during his time as archbishop. The precise nature of Oskytel's and Oswald's relationship is unclear, but they were relatives.
He died on 1 November 971 or on 31 October 971 at Thame, and was buried at Bedford.
There is an entry in the Anglo-Saxon Chronicle for the year 970 or 971, which says:
This year died Archbishop Oskytel; who was first consecrated diocesan bishop at Dorchester, and afterwards it was by the consent of King Eadred and all his council that he was consecrated Archbishop of York. He was bishop two and twenty winters; and he died on Allhallow-mas night, ten nights before Martinmas, at Thame. Abbot Thurkytel, his relative, carried the bishop's body to Bedford, because he was the abbot there at that time.