Middle leaders in schools are increasingly recognised as playing pivotal roles in school improvement. Although some school systems provide formal professional development for middle leaders, many middle leaders express a preference for job-embedded learning. Yet, international research has documented difficulties in providing intensive support from principals which instead is often ad hoc. This study examines how middle leaders' professional learning can be supported through the development of appropriate organisational structures. It presents three principal-designed models distilled from qualitative data collected in 12 case study schools, inclusive of public, semi-private, and international schools in four East Asian societies. Each model contributed to the development of middle leadership capacity in areas relevant to the schools' improvement agendas. The models vary in degrees of formality, resource intensiveness, and processes for engaging and developing leadership. The findings contribute to the growing literature on middle leader development, and the role of school infrastructure in professional learning by suggesting how school-based leader development strategies can be framed in coherent and intentional models that take into account of the available infrastructure and potential professional interactions to provide systematic in situ support for middle leaders.