The following is from the Oxford University site - link below:

Women were originally granted limited admission to the University of Oxford with the founding of the five women's halls in the late nineteenth century. Lady Margaret Hall and St Anne's were founded in 1878, followed by Somerville in 1879, St Hugh's in 1886 and St Hilda's in 1893. Women were granted full membership of the University, and were first awarded full degrees, in 1920. Five colleges - Brasenose, Jesus, Wadham, Hertford and St Catherine's - first admitted women in 1974, and today only St Hilda's, which is for women only, remains single-sex.