This article develops a theory of late stage group performance based on the late stage group’s unique characteristics: a long shared history, an indefinite endpoint, a long member entry/exit history, and a long “parent” organization relationship. These characteristics are markedly different from those of earlier stage groups, suggesting that extant literature’s limited “maintenance” or “cyclical” prescriptions are insufficient for effective late stage group management. Six propositions are developed to model the relationship between late stage group characteristics and performance. Managerial implications are also discussed and a late stage group research agenda is proposed.