Winfrey, probably the most powerful woman in the U.S. entertainment business, spoke for more than an hour to a crowd of 4,500 people after receiving the degree Friday afternoon, the Mail & Guardian Online reported.
She also brought five members of the university's housekeeping staff to the stage, the Chicago Sun-Times said.
Winfrey's involvement with the university began when she learned of a racist video made five years ago by four white students. On the video, the students pretended to put urine in stew to be eaten by black housekeepers and talked of how the university should not be integrated.
Jonathan Jansen, who became the university's first black rector in 2009, called for forgiveness instead of punishment.
Winfrey said that after reading a column by Jansen she called John Samuel, a university official and former head of the Oprah Winfrey Leadership Academy for Girls in South Africa.
"Could you please tell Professor Jansen that I read this article, and I love him and I love this article," said Winfrey. "And John said no, you can tell him yourself."