Harris' friend, Francesca James, told The New York Times she was with Harris at her home on Cape Cod when she died.
The actress had a long career, becoming a theater star in 1950 when she was 24. She played the 12-year-old Frankie in Carson McCullers' "A Member of the Wedding," a role she reprised in the movie.
Almost 50 years later, in 1997, she received her 10th and last Tony nomination for a revival of "The Gin Game." She was awarded a special Tony for lifetime achievement in 2002, bringing her total to six.
She appeared in a few movies after suffering a 2001 stroke, playing a stroke victim in one of them.
On stage, she played Shakespeare, modern classics and even appeared in a musical, although a reviewer said her voice would not be mistaken for Ethel Merman's. She was the first Sally Bowles, in the play "I Am A Camera," which was later adapted into the musical "Cabaret."
John van Druten, who adapted the play from a book by Christopher Isherwood, compared her to a clear glass pitcher in a 1955 interview with the Times.
"You pour in red wine, the pitcher looks red; pour in creme de menthe, it is green," van Druten said. "When she's by herself, Julie's almost transparent, almost non-existent."
In movies, she acted with James Dean in "East of Eden" and Claire Bloom in "The Haunting." In addition to her eight-year run as a country singer on "Knots Landing," she appeared in "Hallmark Hall of Fame" specials and in guest roles in many television shows as well as starring in two short-lived series.
Harris was named a recipient of the Kennedy Center Honors in 2005.
Offstage, Harris was married and divorced three times and had one son, Peter Gurian, with her second husband.