In 1964, he left Illinois to become vice president of academic affairs at the University of California, Irvine.

Peltason served as UC president for the last three years of his long career.

First, in more prosperous times, UC had approved generous deferred compensation for its chancellors and other top executives which was no longer politically defensible during the early 1990s recession, and Peltason was forced to spend a great deal of time on the tasks of trimming back UC's executive salary and benefits programs and defending them to the public.

[2] Second, in 1994, Regent Ward Connerly and Governor Pete Wilson launched a campaign to prohibit the use of affirmative action in UC admissions.

Despite strong opposition from Peltason and most UC senior executives (including UCSF associate dean and future UC President Michael V. Drake),[3] Connerly and Wilson were able to persuade a majority of the Board of Regents to approve two resolutions to that effect on July 20, 1995.