Teacher professional development is a complex enterprise (Sprinthall, Reiman, and Thies-Sprinthall, 1996). While many online professional development programs have been introduced over the past several years that provide continuous, job-embedded support, empirical evidence relating what works and what does not has been limited (Whitehouse, Breit, McCloskey, Ketelhut, & Dede, 2006). This study examined the case of a practice-based, task-oriented, online teacher professional learning community designed to further develop participants' knowledge and understanding of coaching teacher inquiry/action research. Using activity theory as an analytical framework, this study looked at the ways in which participation in an online learning community (as a teacher professional development organizational structure) supported/hindered participants' abilities to (1) deepen their understanding of the teacher inquiry/action research process; (2) deepen their understanding of coaching teacher inquiry/action research; and (3) deepen their understanding of their own evolving stance toward their coaching practice. The various motivations that brought participants to the online learning community translated into ways of acting that helped to explain how and why the community functioned. The study's findings showed that participants perceived value in the online learning community as a communication medium that supported collaborative learning and knowledge production. Ultimately, this study identified specific actions and roles within which teachers' learning can be meaningfully situated online, offering insight into the application of online learning communities for professional development purposes. It is hoped that this study will be helpful to those who facilitate online communities as well as those who seek such communities for growth and inspiration. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]