Mariclare Costello lived a life that moved between stages, screens, classrooms, and communities with the same quiet authority. The actress, born February 3, 1936, in Peoria, Illinois, died April 17, 2026, in Brooklyn, at the age of 90. She leaves behind a career of remarkable range and a legacy that extended well beyond any single role.
Most audiences knew her as Rosemary Hunter on CBS’s The Waltons, where she appeared in 15 episodes across the show’s first five seasons. Her character, the schoolteacher who eventually married the Rev. Matthew Fordwick (John Ritter), was warm and grounded, exactly the qualities Costello brought to everything she did. “I had the greatest time with Richard Thomas and John Ritter,” she recalled in a 2011 interview. “We laughed from the beginning of the day until the end of the day.”
Horror fans claimed her just as firmly. Her turn as Emily Bishop in the 1971 cult film ‘Let’s Scare Jessica to Death,’ a hippie-vampire who rises from a lake in a wedding dress, remains one of the genre’s most haunting performances. It’s the kind of role that follows an actress forever, and Costello wore it well.
Her theatrical roots ran deep. She studied improv with Viola Spolin at Catholic University, earned her master’s in Theater and Education, and performed for President Kennedy as Nerissa in a production of ‘The Merchant of Venice.’ In 1964, she was among just 30 actors selected for the original Lincoln Center Repertory Company, where she originated the role of Louise in Arthur Miller’s ‘After the Fall,’ directed by Elia Kazan, opposite Jason Robards.
Broadway followed, four times over, including a 1970 revival of ‘Harvey’ alongside Jimmy Stewart and Helen Hayes, and an early production with Stacy Keach. She was a lifetime member of The Actors Studio, and trained alongside Jerome Robbins, James Earl Jones, Faye Dunaway, Hal Holbrook, and Austin Pendleton.
Her television work spanned decades. She appeared in ‘Ordinary People,’ ‘The Adventures of Buckaroo Banzai Across the 8th Dimension,’ ‘Raid on Entebbe,’ and episodes of Ironside, Kojak, Lou Grant, Murder She Wrote, Chicago Hope, and Judging Amy. In 1974, she played the wife of Martin Sheen’s title character in the Emmy-winning telefilm ‘The Execution of Private Slovik.’ Each credit was another proof of her versatility.
After her on-screen career wound down, she poured that same energy into teaching. She led the drama program at St. Paul the Apostle Elementary School in Westwood, directed at Loyola High School and Loyola Marymount University, and led a theater group at Homeboy Industries, the largest gang rehabilitation and re-entry program in the world. Her basement was filled floor to ceiling with costumes and props. Her productions, by all accounts, were works of extraordinary care.
She met her husband, actor Allan Arbus, in an acting class taught by Mira Rostova. They fell in love rehearsing a Dorothy Parker one-act, moved to Los Angeles in the late 1960s, and married at home in 1977 after twelve years together. Arbus died in 2013. The last production she saw was ‘Waiting for Godot,’ directed by her daughter Arin at Theater for a New Audience.
Costello is survived by her daughter Arin and her partner Ethan, granddaughter Bird, step-daughters Amy and Doon, and her nieces and nephew.