He retired from the position of Speaker and from parliament in 1761, and enjoyed an annuity of £3000 until his death. As Speaker, Onslow was a conspicuous success, displaying knowledge, tact and firmness in his office; in his leisure hours he was a collector of books.
Speaker Onslow's nephew, George Onslow (1731_1792), a son of his brother Richard, was a lieutenant_colonel and member of parliament for Guildford from 1760 to 1784. He had a younger brother Richard (1741_1817), who entered the navy and was made an admiral in 1799.