This is a study of teachers' authentic professional learning at a public school in Poudre School District in northern Colorado. At Polaris Expeditionary Learning School, teachers and administrators have developed a form of school-based instructional rounds referred to herein as PLC rounds (professional learning community rounds). In PLC rounds, Polaris teachers visit their colleagues' classrooms in teams to observe and interact with the host teacher and students. Afterwards, observing teachers reflect on their observations and interactions and engage in professional dialogue about how the experience might inform their practice. These dialogues become part of a larger conversation across all rounds teams in service of school improvement. Despite increased interest in school-based instructional rounds as a professional learning approach, a theory-research gap persists. This study draws upon teachers' lived experiences by encouraging them to reflect on their participation in PLC rounds. Through interviews and analysis, a theoretical framework is constructed to explain this dynamic phenomenon. The study distinguishes the PLC rounds approach from other forms of instructional rounds, outlines its key components, articulates teachers' professional learning experiences, explores this learning in relation to the strengthening of the professional learning community, and identifies practices that support and hinder their professional learning. In addition, it contributes insights for local practice at Polaris, considerations for interested schools and/or school districts, and recommendations for future research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]