His first big break came when he was hired in New York City by Charles Mingus as a replacement for Jackie McLean in the 1960s. His brief stint with the eccentric bass player made a deep impression. Mingus' sparing use of notation and his belief that there was no such thing as a wrong note had a lasting influence on Green's own style.
The next year, Green moved to Chicago where he appeared with several prominent players including Sonny Stitt, Louie Bellson, Andrew Hill, Yusef Lateef, and Ira Sullivan. Originally strongly influenced by Charlie Parker, Green spent a period reassessing his style and studying, emerging with a much more distinctive sound.
Green gradually withdrew from the public eye to develop a career as a leading jazz educator. He taught at Chicago State University from 1972-1989, and in the 1990s took up the directorship of the jazz studies programme at the University of North Florida in Jacksonville. He has also served a term as the president of the International Association of Jazz Educators and been elected to the Jazz Education Hall of Fame.
As a result of his educational activities, Green has only released a few sessions since the mid-1960s. His 1989 session, Healing The Pain, commemorates the death of his parents.