After a couple of other plays, she segued to features with a supporting role as Beau Bridges' sister in Hal Ashby's "The Landlord" (1970). Later that year, she earned notice for a steamy scene with Jack Nicholson in "Five Easy Pieces". Her subsequent feature appearances have been sporadic. Anspach hit her peak as the leading lady in Paul Mazursky's "Blume in Love" (1973) and was superb in Dusan Makavayev's disturbing, hilarious "Montenegro" (1981). The actress ventured into TV with such efforts as "I Want to Keep My Baby" (CBS, 1976) and the miniseries "James A. Michener's 'Space'" (CBS, 1985). She twice tried series work but both times the vehicle failed to catch on with the public: the primetime soap "The Yellow Rose" (NBC, 1983-84) and the dramedy "The 'Slap' Maxwell Story" (ABC, 1987-88). As she entered into middle age, good roles became fewer and she channeled her creative energies to teaching.
More recently, Anspach was in the news because of an ongoing dispute with actor Jack Nicholson. The two purportedly engaged in an off-screen romance and Anspach has maintained that her son Caleb was fathered by Nicholson, a claim which the actor reportedly acknowledged privately. It was when the matter became public thanks in part to a letter Anspach wrote to VANITY FAIR magazine in 1994 responding to a profile of Nicholson. Shortly thereafter, she claimed that the actor, who had loaned her money, demanded repayment. Her response was to take legal action. The case eventually was settled with Anspach retaining her home.