McWilliams died Feb. 11 at her home in Los Angeles from complications of multiple myeloma, her family said.
Caroline Margaret McWilliams was born April 4, 1945, in Seattle but grew up in Barrington, R.I. She graduated in 1966 with a bachelor's degree from Carnegie Mellon University in Pittsburgh.
Her first break on television was on "Guiding Light," a longtime CBS soap opera in which she appeared for several years beginning in 1969. While in New York, she also started to build her stage career.
McWilliams' credits included "Boccaccio," "Cat on a Hot Tin Roof" and "The Rothschilds," along with productions for the New York Shakespeare Festival and the American Shakespeare Festival in Stratford, Conn.
She also appeared on the soap opera "Another World" in 1975.
In 1978 and '79, she played Sally on the ABC comedy "Soap," and from 1979 to '81 played Marcy Hill on the series “Benson,” a spinoff from "Soap" starring Robert Guillaume.
Other TV appearances included starring in the 1989 series "Nearly Departed" with Eric Idle, "Beverly Hills, 90210" and "Judging Amy."
Her movie roles included "Mermaids" in 1990.
McWilliams' sister Kelly-Jo Dvareckas said she "really felt she hit her stride when she started to direct."
McWilliams' credits as a director included the plays "Divorcons (Let's Get a Divorce)," "You Haven't Changed a Bit and Other Lies" and "The Smoke and Ice Follies."
In addition to her sister, McWilliams is survived by her son, Sean Douglas, and sisters Norma Liedtke and Patti McWilliams. She was divorced from actor Michael Keaton.