In this chapter, we highlight the importance of the behavioural perspective to advance the discipline of operational research (OR). The power of this perspective lies in its ability to identify the conditions under which the impact of OR-supported processes is enhanced or hindered by behavioural factors, with a view to developing more effective OR practice. To help organise and guide the conduct of empirical studies in the sub-discipline of behavioural OR (BOR), we draw on practice theories from the social and organisational sciences to propose an integrative framework based on the three central concepts of OR methods, OR actors, and OR praxis. In discussing these concepts, we refer to the developing empirical BOR literature to highlight alternative analytical foci. We end the chapter by discussing the implications of the behavioural perspective for advancing the OR discipline, particularly with regards to foregrounding OR praxis in academic papers, attending to a wide diversity of OR actors, developing OR competences, and the role of theory and research methodology.