The bulk of current research on teacher professional development is focused on teacher learning in the context of teacher professional learning communities (PLCs). In teacher PLCs, groups of teachers meet regularly to increase their own learning and the learning of their students. Teacher PLCs offer a learning model in which, "new ideas and strategies emerge, take root, and develop, and where competence can be truly cultivated and nurtured." Research on teacher professional development has recognized the nature of situated learning in the context of teacher PLCs. Situative perspectives of teacher learning can provide a multi-focal research lens, affording the study of multiple units of analysis: the individuals, the community context, and the social interactions of teachers as they develop knowledge for teaching. In this study, the author focused on the situated nature of teacher learning in a PLC that was based on the lesson study model for teacher professional development. Her primary units of analysis were the engagements of four middle school language arts teachers as they participated in a lesson study focused on teaching and learning writing. This study addressed the following research questions: What is the nature of participants' situated engagements in their collaborative inquiry about teaching and learning writing? How did these engagements contribute to transformations in teacher perspectives and pedagogy? The author's findings are discussed in the following themes, which emerged from the data: (a) Participants synthesized their own and each others' prior knowledge, experiences, and resources from diverse theoretical frameworks in teaching and learning writing; and (b) As they negotiated theoretical tensions in teaching and learning writing, participants experienced transformations in their perspectives and pedagogy.