O’Casey is both the Abbey’s most-produced playwright and also an Abbey writer who in a period of a decade or so submitted eleven plays, more than half of which were initially rejected. In O’Casey’s own often tetchy account of this relationship, the rejections are deplorable failures to recognise his genius, and some version of that view has been adopted by much O’Casey scholarship over the years. However, this chapter acknowledges the other side of this story, looking at the extent to which the Abbey in the 1920s functioned as a repertory theatre, part of whose institutional mission involved the mentoring and development of emerging writers.