Mariclare Costello, the warm-hearted character actress who became a fixture in millions of American living rooms as the kindly schoolteacher Rosemary Hunter on CBS’ beloved family drama “The Waltons,” has died. She was 90.
Costello died on Friday, April 17, 2026, in Brooklyn, her family announced. Though best remembered for her recurring role on “The Waltons,” her career stretched across six decades, from the stages of Broadway to cult horror cinema, prestige telefilms and Oscar-winning dramas.
From Peoria to the Bright Lights
Born February 3, 1936, in Peoria, Illinois, Costello was the youngest of three sisters in a family that prized creativity. She attended Clarke College in Iowa before earning a master’s degree in theater and education from Catholic University, where she trained in improvisation under the legendary Viola Spolin. During her years in Washington, she performed for President John F. Kennedy as Nerissa in a production of “The Merchant of Venice.”
After graduate school, Costello moved to New York City, where she became an original member of the Lincoln Center Repertory Company and a lifetime member of The Actors Studio. The stage proved to be her first love. She made her Broadway debut in 1964 in Arthur Miller’s “After the Fall,” opposite Jason Robards, kicking off a remarkable run of nine Broadway productions between 1964 and 1970.
Her Broadway credits piled up quickly: “But For Whom Charlie” (1964), “The Changeling” (1964), “Tartuffe” (1965), “Danton’s Death” (1965), “The Country Wife” (1965), “Lovers and Other Strangers” (1968), “A Patriot for Me” (1969), and a revival of “Harvey” alongside James Stewart and Helen Hayes in 1970.
Hollywood and a Cult Horror Classic
Costello made her film debut in 1967’s “The Tiger Makes Out,” appearing alongside Eli Wallach and Anne Jackson. Television roles followed, but it was a low-budget 1971 horror film that would secure her a permanent place in genre history.
In “Let’s Scare Jessica to Death,” Costello played the pivotal role of Emily, a free-spirited hippie who takes up with Jessica (Zohra Lampert) and her husband, only to reveal herself as a vampire. The image of Costello’s undead character rising slowly from a misty lake remains one of the most haunting moments in 1970s horror, and the film has only grown in cult stature in the decades since.
She continued building an impressive screen résumé, playing the wife of Martin Sheen’s title character in the acclaimed 1974 telefilm “The Execution of Private Slovik.” In 1980, she appeared in Robert Redford’s Oscar-winning “Ordinary People” as the sympathetic sister-in-law of Mary Tyler Moore’s grieving mother.
Walton’s Mountain and a Lasting Legacy
For TV audiences, however, Costello will forever be Miss Rosemary Hunter, the gentle Walton’s Mountain schoolteacher who recognizes a young John-Boy Walton’s literary spark and encourages him to pursue writing. She appeared in the role across five seasons of “The Waltons” between 1972 and 1977, and her character eventually married the Rev. Matthew Fordwick, the town’s preacher played by a pre-“Three’s Company” John Ritter.
She also starred as the family matriarch on the single-season 1977 CBS drama “The Fitzpatricks,” and her episodic TV credits spanned the 1970s, ’80s and ’90s, including “Ironside,” “Kojak,” “Little House on the Prairie,” “Lou Grant,” “Murder, She Wrote,” “Santa Barbara,” “Chicago Hope,” “Judging Amy” and “Providence.”
A Life Beyond the Screen
Costello met her future husband, “M*A*S*H” actor Allan Arbus, in an acting class taught by Mira Rostova, and the two fell in love while rehearsing a Dorothy Parker play. They married in 1977 and remained together until his death in 2013.
Friends and family remembered her not only as a performer but as a teacher, mentor, wonderful cook and animal lover whose curiosity colored every corner of her life. “She was also, in every dimension of her life, someone who paid attention,” her family wrote. “She could talk to anyone, was interested in everything, and was a relentless asker of questions.”
Costello is survived by her daughter, the stage director Arin Arbus, and Arin’s partner, the playwright Ethan Lipton; her granddaughter, Bird; and stepdaughters Amy and Doon. A funeral service will be held in New York City, with burial and a remembrance to follow in her hometown of Peoria.