Parrish was born Ruby Joyce Wilbar on October 21, 1940 in Middlesboro, Kentucky to William Robert "Bob" Wilbar (1913-1988) and Gladys Wilbar (nee Gladys Marie Webb, 1911-1998). She had five younger siblings, sisters Barbara, Janice, and Liza and brothers James and Robert. She spent her early years in Lake City, Tennessee (now Rocky Top, Tennessee), before moving to Tecumseh, Michigan at age 11. There she graduated from high school. Parrish then attended a modeling school in Toledo, Ohio. She won a national contest for "Young Model of The Year" at a modeling school chain.
Parrish first appeared as an actress in the Jerry Lewis movies It's Only Money (1962) and The Nutty Professor (1963), and in a small role in Harlow (1965). After some guest appearances on television series, and roles in films such as Winter A-Go-Go (1965) and Fireball 500 (1966), she co-starred with Elvis Presley in Paradise, Hawaiian Style (1966). Her later film credits included roles in The Doberman Gang (1972), The Time Machine (1978) and The Devil and Max Devlin (1981).
Parrish also made guest appearances in many television series such as Death Valley Days, Gunsmoke, Family Affair, Star Trek, Bonanza, Capitol and Beverly Hills, 90210. She had lead roles on several television soap operas and was the female lead in the short-lived 1967 CBS Television sitcom, Good Morning, World.
Parrish's theater credits include Absence of a Cello and Memo. In Los Angeles, she received an L.A. Drama Critics Award for her portrayal of Maggie in Arthur Miller's After the Fall. She was also a writer and contributed essays, articles, and book reviews to many publications. Parrish began undergraduate studies in her late forties, earning a degree in Chemical Dependencies Counseling. She worked for nine years as a full-time on-staff counselor at the Haven Hills Shelter for Battered Women.