Huckle (2004) has argued that Critical Realism (CR) can provide a philosophical framework for higher education for sustainability by providing a philosophy of knowledge ″that integrates the natural and social sciences and the humanities...supports critical pedagogy, and continues to regards education as a form of enlightenment linked to a vision of more sustainable futures″ (34). His argument is based on the depth ontology of CR and its potential to provide an ontological grounding for interdisciplinary approaches to (SD) and education for sustainable development (EESD). This depth ontology encourages us to look beyond the surface appearance of things to uncover their generative causes. In this paper our focus is on how CR impacts research design and how we used the logic of CR to examine engineering education for sustainable development (EESD) in a limited number of programmes in three institutions in Ireland. Some results of different phases of this work have been reported previously (Nicolaou and Conlon 2012, 2013, 2015, Nicolaou, Conlon and Bowe 2015). In this paper we seek to integrate the findings and provide an account of how our approach was influenced by CR.