Hershey's acting debut, three episodes of Gidget, was followed by the short-lived television series The Monroes (1966), which also featured Michael Anderson, Jr. By this point, she had adopted the stage name "Barbara Hershey".
Although Hershey said the series helped her career, she expressed some frustration with her role, saying: "One week I was strong, the next, weak".
While on the series, Hershey garnered several other roles, including one in Doris Day's final feature film, With Six You Get Eggroll.

In 1969, Hershey co-starred in the Glenn Ford Western Heaven with a Gun.
On the set, she met and began a romantic relationship with actor David Carradine, who later starred in the television series Kung Fu (see Personal life).
In the same year, she acted in the controversial drama Last Summer, which was based on Evan Hunter's eponymous novel.
In this film, Hershey played Sandy, the "heavy" who influences two young men (played by Bruce Davison and Richard Thomas) to rape another girl, Rhoda (played by Catherine Burns).
Though the film, directed by Frank Perry, received an X rating for the graphic rape scene, Burns earned a Best Supporting Actress Oscar nomination for her performance.

During the filming of Last Summer, a seagull was killed. "
In one scene," Hershey explained, "I had to throw the bird in the air to make her fly.
We had to reshoot the scene over and over again.
I could tell the bird was tired.
Finally, when the scene was finished, the director, Frank Perry, told me the bird had broken her neck on the last throw."
Hershey felt responsible for the bird's death and changed her stage name to "Seagull" as a tribute to the creature. "
I felt her spirit enter me," she later explained. "
It was the only moral thing to do."
The name change was not positively received.
When she was offered a part opposite Timothy Bottoms in The Crazy World of Julius Vrooder (1974) (or Vrooder's Hooch), Hershey had to forfeit half her salary, $25,000, to be billed under the name "Seagull" because the producers were not in favor of the billing.
Hershey's acting debut, three episodes of Gidget, was followed by the short-lived television series The Monroes (1966), which also featured Michael Anderson, Jr. By this point, she had adopted the stage name "Barbara Hershey". Although Hershey said the series helped her career, she expressed some frustration with her role, saying: "One week I was strong, the next, weak". While on the series, Hershey garnered several other roles, including one in Doris Day's final feature film, With Six You Get Eggroll.
In 1969, Hershey co-starred in the Glenn Ford Western Heaven with a Gun. On the set, she met and began a romantic relationship with actor David Carradine, who later starred in the television series Kung Fu (see Personal life). In the same year, she acted in the controversial drama Last Summer, which was based on Evan Hunter's eponymous novel. In this film, Hershey played Sandy, the "heavy" who influences two young men (played by Bruce Davison and Richard Thomas) to rape another girl, Rhoda (played by Catherine Burns). Though the film, directed by Frank Perry, received an X rating for the graphic rape scene, Burns earned a Best Supporting Actress Oscar nomination for her performance.
During the filming of Last Summer, a seagull was killed. "In one scene," Hershey explained, "I had to throw the bird in the air to make her fly. We had to reshoot the scene over and over again. I could tell the bird was tired. Finally, when the scene was finished, the director, Frank Perry, told me the bird had broken her neck on the last throw." Hershey felt responsible for the bird's death and changed her stage name to "Seagull" as a tribute to the creature. "I felt her spirit enter me," she later explained. "It was the only moral thing to do." The name change was not positively received. When she was offered a part opposite Timothy Bottoms in The Crazy World of Julius Vrooder (1974) (or Vrooder's Hooch), Hershey had to forfeit half her salary, $25,000, to be billed under the name "Seagull" because the producers were not in favor of the billing.
Barbara Hershey