With this success, and now based in Berkeley, Zaentz made an auspicious entry into feature film production with Milos Forman's "One Flew Over the Cuckoo's Nest" (1975). Starring Jack Nicholson and based on Ken Kesey's underground classic, the film became one of the biggest--and unlikeliest--critical and commercial smashes of the day, becoming the second picture to earn Oscars in the top five categories, including one for Best Picture Oscar for Zaentz and co-producer Michael Douglas.
Zaentz's subsequent efforts, often literary adaptations, have been infrequent, but usually been worth the wait. A reteaming with director Forman in 1984 on "Amadeus", based on Peter Shaffer's play about Mozart, yielded a second Best Picture Oscar. Philip Kaufman's "The Unbearable Lightness of Being" (1988), featured Strong central performances from Daniel Day-Lewis and Juliette Binoche and introduced Lena Olin to American audiences. He stumbled with the adaptation of "At Play in the Fields of the Lord" (1991), directed by Hector Babenco. While the film has much to admire, its length and subject left audiences cold and resulted in a loss of some $20 million, a costly one for the producer. Zaentz, however, rebounded with Anthony Minghella's "The English Patient" (1996), a stirring epic with stunning visuals and brilliant performances, adapted from Michael Ondaajte's novel. The film earned 12 Oscar nomination and won a total of nine, including Best Picture. For his overall efforts, Zaentz was also selected by the Academy of Motion Picture Arts and Sciences to receive the 1996 Irving G Thalberg Award.
In the early 80s, he founded the Saul Zaentz Company Film Center, a post-production sound facility, that has become a valuable resource for the northern California filmmaking community.