Discovered in a student production at Hollywood High School, she soon found herself on TV befriending Sally Field's "Gidget" before moving on to a regular role on "The Monroes" (ABC, 1966-67), a Western series. With her ability to convey an appealing blend of innocence and sensuality, Hershey was typecast in "flower child" roles in features until she won rave reviews for her performance opposite Peter O'Toole in "The Stunt Man" (1980).

Hershey starred as the title character in Martin Scorsese's first feature, "Boxcar Bertha" (1972). Her free spirited 60s persona somehow worked for the 30s milieu of this superior Roger Corman potboiler. During the filming, Hershey gave Martin Scorsese a copy of her favorite novel, Nikos Kazantzakis' "The Last Temptation of Christ". She wanted to play the part of Mary Magdalene, which she did 16 years later when Scorsese made the film for Universal.

Hershey hit her stride in the subsequent decade, acting in numerous superior films of the 80s (e.g., Philip Kaufman's "The Right Stuff" 1983; Barry Levinson's "The Natural" 1984; Woody Allen's "Hannah and Her Sisters" 1986; and Martin Scorsese's "The Last Temptation of Christ" 1988). Hershey was the first to win two consecutive Best Actress awards at the Cannes Film Festival: for Andre Konchalovsky's "Shy People" (1987) and Chris Menges' "A World Apart" (1988). She has also worked extensively in TV, most impressively in the high-toned "A Killing in a Small Town" (CBS, 1990), for which she won an Emmy, "Paris Trout" (Showtime, 1991) and the miniseries "Return to Lonesome Dove" (CBS, 1993).

Hershey has kept busy in features appearing in "Tune in Tomorrow" (1990), "Defenseless" (1991), "The Public Eye" (1992), "Falling Down" and "Swing Kids" (both 1993). She had one of her best screen roles in recent years as the mother of a recently deceased young man who seduces one of his friends in "The Pallbearer" (1996). Later that year, she co-starred in Jane Campion's film adaptation of the Henry James' novel "Portrait of a Lady".