The constituency comprised the whole of the historic county of Oxfordshire, in the northern part of South East England. (Although Oxfordshire contained three parliamentary boroughs for part of this period – Oxford (from 1295), Woodstock (or New Woodstock) (1302–1555 and from 1571) and Banbury (from 1554) – each of which elected MPs in their own right, these were not excluded from the county constituency, and owning property within the borough could confer a vote at the county election. The Oxford University constituency was also often listed as an Oxfordshire constituency, but was non-territorial and had no effect on the right to vote in the county.)
There were minor boundary changes at the time of the Great Reform Act in 1832, when five parishes or parts of parishes were transferred to other counties while six parishes or parts of parishes were added.
The county franchise, from 1430, was held by the adult male owners of freehold land valued at 40 shillings or more. The bloc vote electoral system was used in two seat elections and first past the post for single member by-elections. Each elector had as many votes as there were seats to be filled. Votes had to be cast by a spoken declaration, in public, at the hustings, which took place in Oxford. The expense and difficulty of voting at only one location in the county, together with the lack of a secret ballot contributed to the corruption and intimidation of electors, which was widespread in the unreformed British political system.
The expense, to candidates and their supporters, of contested elections encouraged the leading families of the county to agree on the candidates to be returned unopposed whenever possible. Contested county elections were therefore unusual. The Tory Dukes of Marlborough, dominated the county from their seat at Blenheim Palace. One seat was usually held by a Spencer, the other by a local family acceptable to the Duke. Between 1700 and 1826 there was only one contest.
Note on percentage change calculations: Where there was only one candidate of a party in successive elections, for the same number of seats, change is calculated on the party percentage vote. Where there was more than one candidate, in one or both successive elections for the same number of seats, then change is calculated on the individual percentage vote.
Note on sources: The information for the election results given below is taken from Stooks Smith 1715–1754, Namier and Brooke 1754–1790 and Stooks Smith 1790–1832. From 1832 the principal source was Craig, with additional or different information from Stooks Smith included.
Wenman was a Peer of Ireland. There was a double return (of all four candidates) after the most hotly contested county election of the century. The disputed election was decided by the House of Commons on petition, with Parker and Turner being declared duly elected on 23 April 1755.
Note (1852): The minimum possible turnout is estimated by dividing the number of votes cast by three. To the extent that electors did not use all their three possible votes the figure given will be an underestimate of the true turnout
Boundaries of Parliamentary Constituencies 1885–1972, compiled and edited by F.W.S. Craig (Parliamentary Reference Publications 1972)
British Parliamentary Election Results 1832–1885, compiled and edited by F.W.S. Craig (Macmillan Press 1977)
The House of Commons 1754–1790, by Sir Lewis Namier and John Brooke (HMSO 1964)
The Parliaments of England by Henry Stooks Smith (1st edition published in three volumes 1844–50), second edition edited (in one volume) by F.W.S. Craig (Political Reference Publications 1973)) out of copyright
Who's Who of British Members of Parliament: Volume I 1832–1885, edited by M. Stenton (The Harvester Press 1976)
Who's Who of British Members of Parliament, Volume II 1886–1918, edited by M. Stenton and S. Lees (Harvester Press 1978)