 From 1740 to 1741, he was Grand Master of the Premier Grand Lodge of England, Governor of County Clare from 1741 to 1777 and Custos Rotulorum of Clare from 1762 to 1767.From 1744 to 1751, he was a Lord of the Bedchamber to Frederick, Prince of Wales, and admitted to the Privy Council of Ireland in 1753.On his death in 1777, without surviving male heirs, his titles passed to his nephew, Murrough O'Brien, who was later created Marquess of Thomond.