The company moved from San Francisco to New York City, and Collier was replaced as publisher by Roger Kimball.
Returning to California, Collier taught Freshman English at UC Berkeley from 1964 to 1969 and again as a Visiting Writer from 1977 to 1981.
Collier was teaching at the University of California, Berkeley, in 1966 when he became an editor at radical Leftist Ramparts magazine, the splashy, four-color publication that was influential in transmitting New Left ideas into the mainstream.
As the Vietnam War came to an end, he and fellow Ramparts writer David Horowitz became disillusioned when the New Left turned a blind eye to the atrocities committed by the communist victors in Southeast Asia—the tiger cages and boat people in South Vietnam, the genocide in Cambodia.
[3] Collier and Horowitz traveled to Nicaragua in 1987 at the invitation of the State Department to encourage the "civic resistance" against the Sandinistas.
[4] The same year they organized a "Second Thoughts Convention" in Washington D.C. Their book about leaving the Left and becoming its enemies, Destructive Generation (1989), was compared to Whittaker Chambers' Witness.