This recommended Robert Harley to the notice of the Boscawen family, and led to his election, in April 1689, as the parliamentary representative of Tregony, a borough under their control, whilst at the same time acting as High Sheriff of Herefordshire. He sat for Tregony for one parliament, after which, in 1690, he was elected by the constituency of New Radnor, which he represented until his elevation to the peerage in 1711. From an early age, Harley paid particular attention to the conduct of public business, taking special care over the study of the forms and ceremonies of the House of Commons.