Answer by taking a quote from the following article:

William Jefferson Clinton (ne Blythe III; born August 19, 1946) is an American politician who served as the 42nd President of the United States from 1993 to 2001. Prior to the presidency, he was the Governor of Arkansas from 1979 to 1981, and again from 1983 to 1992. A member of the Democratic Party, Clinton was ideologically a New Democrat and many of his policies reflected a centrist "Third Way" political philosophy. Clinton was born and raised in Arkansas and attended Georgetown University, the University of Oxford, and Yale Law School.

Upon graduating from Georgetown in 1968, Clinton won a Rhodes Scholarship to University College in Oxford, England, where he initially read for a B.Phil. in Philosophy, Politics, and Economics but transferred to a B.Litt. in politics and, ultimately, a B.Phil. in politics. Clinton did not expect the second year because of the draft and he switched programs; this type of activity was common among other Rhodes Scholars from his cohort. He had received an offer to study at Yale Law School, Yale University, but he left early to return to the United States and did not receive a degree from Oxford.  During his time at Oxford, Clinton befriended fellow American Rhodes Scholar Frank Aller. In 1969, Aller received a draft letter that mandated deployment to the Vietnam War. Aller's 1971 suicide had an influential impact on Clinton. British writer and feminist Sara Maitland said of Clinton, "I remember Bill and Frank Aller taking me to a pub in Walton Street in the summer term of 1969 and talking to me about the Vietnam War. I knew nothing about it, and when Frank began to describe the napalming of civilians I began to cry. Bill said that feeling bad wasn't good enough. That was the first time I encountered the idea that liberal sensitivities weren't enough and you had to do something about such things". He also developed an interest in rugby union, which he played at Oxford.  While Clinton was president in 1994, he received an honorary degree and a fellowship from the University of Oxford, specifically for being "a doughty and tireless champion of the cause of world peace", having "a powerful collaborator in his wife," and for winning "general applause for his achievement of resolving the gridlock that prevented an agreed budget".

What did he study in oxford?
he initially read for a B.Phil. in Philosophy, Politics, and Economics