After his cousin William Hay, 6th Earl of Erroll died in 1541 leaving only a young daughter, George succeeded to the earldom and with it the family title of Lord High Constable of Scotland. The sixth earl, who inherited the earldom as a toddler, died under the age of 21; by the time George inherited the titles, the barony had been in the possession of the crown for 19 years, four months.
The Peerage of Scotland allows titles to descend along the female lines; Jean Hay, the young daughter of the sixth earl of Erroll, could have inherited the earldom as Countess of Erroll. Instead, the crown negotiated for George to inherit, with the condition that he pay 4,000 merks to Helen, Dowager Countess of Erroll and to marry one of his sons to Jean Hay "at the King's pleasure."[2]
Following the death of James V of Scotland in December 1542 leaving six-day-old Mary, Queen of Scots as his successor, Erroll was one of the nobles who signed an agreement to support her mother Mary of Guise taking the Regency. They argued unsuccessfully that the Earl of Arran ought to be disqualified because his father's divorce and second marriage were invalid, making him illegitimate. Arran resigned the Regency to Mary of Guise in 1554.
He had a disagreement with his wife, Margaret Robertson, in 1554. Mary of Guise counseled reconciliation. Margaret Robertson wrote to Mary of Guise from Perth, that he had not restored her living and she might have to come and live at court in her service as a gentlewoman. Erroll claimed she had supported "broken men", landless rebels who stole his goods, but Margaret wrote it ought to be well known that she desired no harm or loss to him or their children. She sent her eldest son, Andrew, Master of Atholl to explain her case more fully.[3]
He was a member of the Privy Council of Mary, Queen of Scots in 1561. He sided with the Hamiltons in the interest of the captive Queen Mary in 1569, but did not forfeit his titles in his support of the queen.[4]
Lady Elizabeth Hay (b. 1531), married firstly Sir William Keith, Lord of Keith, son of William Keith, 4th Earl Marischal and secondly Cuthbert, baron Coulhart