The constructivist grounded theory, actualizing collaborative learning, conceptualizes how British Columbia primary grade teachers interacted with the professional learning endeavour Changing Results for Young Readers (CR4YR). CR4YR was a British Columbia Ministry of Education initiated and co-facilitated cross-school Network Learning Community that included educators from four levels of the school system. While Network Learning Communities, such as the CR4YR initiative, have been increasingly utilized as professional learning models for educators, a review of the literature indicated that questions remained as to how teachers, who were unaccustomed to collaborative learning endeavour, adapted to environments in which vulnerability was the primary learning tool. This study addressed this knowledge gap. The theory, actualizing collaborative learning, emerged from analysis of data gathered through semi-structured interviews with 22 CR4YR participants in five British Columbia school districts. The interviewees included school district administrators, Reading Advocates, and teachers. The resulting theory specifies that collaborative learning in CR4YR was built upon the interaction of the four sub-processes: establishing trust, identifying with collaborative learning, becoming vulnerable, and mobilizing collaboration to the school. The participants’ utilization of the four sub-processes was impacted by three contextual factors which were skilled leadership, interlinking points of contact, and the extended time period allocated for the CR4YR initiative. The theory extends current conceptualizations of professional learning in network learning communities by identifying the contextual factors and sub-processes that support teachers as they acclimatize to collaborative learning in cross-school environments with representation from multiple levels of the school system. / Graduate / wilmot94@telus.net