This Australian study examined the emergence of collaborative processes when introducing co-teaching a unit of work into classroom practice. Six teams of regular and special educators at three primary schools (students aged 6 to 12 years) volunteered to systematically reflect on their co-teaching activities to design, implement, and evaluate a unit of work across the second half of the teaching year. A university-school collaboration scheduled five sessions of action learning in one common school-based location after school hours. Teaching teams and university staff came together in these sessions in order to share perspectives and to document reflections-on-action. Teacher reflections about co-teaching for their respective unit of work and grade level at the start of this project underwent clear changes throughout the educational process from design, implementation, to evaluation. During ongoing co-teaching activities, teachers reorganized their feelings and thoughts about roles and responsibilities in regular classrooms for students with diverse abilities and needs. By the end of the project, moreover, teachers in these teams were engaging in spontaneous choices to embed co-teaching in ongoing practice, to extend their co-teaching into new units of work and into forward planning for students with disabilities coming into a new year's classes, and, more broadly, to advance co-teaching into whole-of-school practice.