Born into a Jewish family in New Jersey, USA, Ross Lazar came to Britain in the early 1970s to train at the Tavistock Clinic in London: he chose the Tavistock because it was a centre of excellence where the Kleinian school of psychoanalysis—grounded in the observation of infants, children and families—had been established. Under the sway of Klein and her talented protégés Wilfred Bion, Esther Bick, Donald Meltzer, and Martha Harris, the Tavistock provided the milieu for learning about and working with Klein's theoretical and clinical contributions, Bick's observational methods, and Bion's application of these ideas to groups and institutions. With supervision from Donald Meltzer and Martha Harris, Ross's training would equip him for an extraordinary career in psychoanalytic psychotherapy, observational studies, group relations and organisational consultancy.

In 1978, Ross moved to Munich, Germany, where he played a pivotal role in spreading the Kleinian approach to continental Europe, and especially Germany. He was well placed to do so, because—at least at