Josephine Clare Barstow was born in Sheffield, England, on September 27, 1940. Her musical studies were at the University of Birmingham, and then at the London Opera Center. She joined Opera for All in 1964. In 1967 and 1968 she performed with the Sadler's Wells Opera, appearing in the role of Cherubino in Mozart's Le Nozze di Figaro. Also in 1967 she joined the Yorkshire Opera, a short-lived company, and from there she joined the Welsh National Opera in 1968, beginning again with the part of Cherubino. She went on to sing the part of the Countess in the same opera with that company. She has frequently sung with the Welsh company and, from 1969, also frequently appeared at Covent Garden, beginning at a typically English starting point, as one of "the Nieces" in Britten's Peter Grimes. She first performed with the Glyndebourne Company in 1972 as Lady Macbeth when that company made a television recording of Verdi's Macbeth; her first actual stage appearance at Glyndebourne was in 1974 as Electra in Mozart's Ideomeneo. Her first appearance with the Metropolitan Opera Company in New York was on March 28, 1977, as Musetta in La Boheme.