Professional learning (PL) for inclusion is a key policy focus internationally, arising from a growing commitment to the goal of a rights-based approach to education for all. Transformative teacher PL for inclusion is paramount to this goal but it is a complex endeavour, as evidenced in the persistent knowledge-practice gap relating to inclusive practice. Models of collaborative inquiry hold promise for affecting teacher change, yet there is limited research on how such models can support quality teacher PL for inclusion. This qualitative cross-case analysis focuses on two models of collaborative inquiry in different contexts in the Republic of Ireland (RoI): a professional learning community (PLC) for inclusive practice in a primary school and an online learning community (OLC) that supported preservice teacher learning during school placement. Parallel findings across the two case studies demonstrated changes in participants’ beliefs, efficacy and practice, arising from collaborative inquiry that was characterised by critical dialogue and public sharing of work. External facilitation of the learning communities supported the creation of a ‘safe space’ which was paramount to transforming PL contexts. We proffer design principles for sustainable collaborative PL approaches across teacher education contexts that support teachers to navigate the complexity of enacting inclusive practice.