Increasingly, professional learning (PL) approaches in the U.S. and globally are reflecting highly adaptive and socially constructed views of learning. However, much remains to be learned about how professional learning groups discursively develop and sustain collaborative communities. Drawing on positioning theory in this year-long qualitative study, we sought to understand how the dialogue used in a literacy teacher learning community shaped how participants engaged in PL. Results revealed that the nature of dialogue within and across social tasks during collaborative PL meetings evolved such that the teachers in the PL community assumed and enacted more agency for their professional learning across the year. Moreover, the evolving storyline of the group across the year was informed by the way discursive practices were enacted in terms of conversant's rights and duties, the social force of their conversational turns, and the evolving identities of individuals and the group. This work matters because the more we understand the characteristics of effective PL approaches, the better we can co-construct effective PL communities with teachers that promote their learning and the learning of their students.