Grist was born in New York City, and grew up in an East River housing project in what we now call Spanish Harlem. She obtained a solid voice training with Claire Gelda, and started singing in Broadway musicals as a teenager. Her first quasi-operatic engagement came in 1956, when she sang the role of Cindy Lou in Oscar Hammerstein's Carmen Jones. She created the role of Consuela in the original production of Leonard Bernstein's classic musical, West Side Story, in 1957, introducing the haunting song "Somewhere" to the public. Her first breakthrough in classical music, came shortly after, when Bernstein invited her to sing the soprano part in Gustav Mahler's fouth symphony.
Her official operatic debut took place at the Santa Fe Opera in 1959, as Adele in Johann Strauss's Die Fledermaus, followed by Blondchen in Mozart's The Abduction from the Seraglio. Shortly after she was invited to the opera of Cologne to sing the Queen of the Night in Mozart's The Magic Flute, which marked her European debut in 1960. She became a regular performer at Zurich Opera where she sang in many light coloratura roles, such as Sophie in Der Rosenkavalier and Zerbinetta in Ariadne auf Naxos. After her success in Zurich, she found herself much in demand, making her debut at the Royal Opera House and the Glyndebourne Festival, in 1962, followed by the Vienna State Opera and the San Francisco Opera, in 1963, the Salzburg Festival, in 1965, where she sang frequently the Mozart soubrette roles, such as Susanna in Le nozze di Figaro, Zerlina in Don Giovanni, and Despina in Cosi fan tutte.
Her Metropolitan Opera debut took place on February 25, 1966, as Rosina in Il barbiere di Siviglia. Her other roles at the Met included, Adina in L'elisir d'amore, Norina in Don Pasquale, Gilda in Rigoletto, Olympia in Les contes d'Hoffmann, Oscar in Un ballo in maschera, as well as Sophie in Der Rosenkavalier and Zerbinetta in Ariadne auf Naxos.
Grist was also active teaching at the Munich Hochschule, and giving numerous masterclasses in centers such as Zurich, Ravinia, Bloomington, San Francisco. She currently lives in Hamburg with her husband, noted musicologist, Ulf Thomson.
Reri Grist possessed a sweet and agile voice, and a most enchanting presence on stage. She made relatively few recordings, but can be heard as Aminta in Il re pastore, opposite Lucia Popp, Blondchen in Die Entfuhrung aus dem serail, opposite Arleen Auger, Gilda in Rigoletto, opposite Cornell MacNeil and Nicolai Gedda, and as Oscar in two recordings of Un ballo in maschera, the first in 1966, opposite Leontyne Price, and the second in 1975, opposite Martina Arroyo, two African-American sopranos like Grist. She appears as Zerbinetta in a Salzburg Festival film of Ariadne auf Naxos (conducted by Karl Böhm, available on DVD) and sang Susanna in Otto Klemperer's recording of Le Nozze die Figaro.