Trends in teacher education increasingly emphasize the need for quality ongoing teacher professional development that is accessible, flexible, fosters advanced skillset development, and has the power to change teachers' practice. Participatory approaches to learning that are situated, collaborative, dialogic, and inquiry-oriented promote the development of such knowledge, skills, and practices within professional communities of practice and form a foundation for quality teacher professional development. Current online and collaborative technologies offer significant access, flexibility, and economic advantages and afford individuals ways to connect with others without time and space restrictions, making online teacher professional development possible. Online learning environments where deep knowledge and complex understanding emerge through dialogue and collaboration within communities of practice must be carefully designed. These learning environments are typically context-dependent, and the design solutions and their implementation may vary substantially. Therefore, these designs must be guided by the most current theoretical understanding and best instructional and design practices. Research in this dissertation adds to our understanding of effective online teacher professional development design, development, and implementation practices by responding to a local problem of redesigning existing teacher professional development courses into an online modality. This dissertation is presented in a three-article format. The first article is an integrative literature review. It contributes by bringing together theories, frameworks, and practices from several different disciplines and could inform online participatory professional development design solutions across various contexts. The second article is a design case featuring a template designed to support progressive knowledge-building discourse, a fundamental feature connecting multiple characteristics that contribute to effective teacher professional development. The third article presents findings from a self-study of design practice. It provides insight into decision-making during purposefully employing technology to meet pedagogical needs during the design process. This study demonstrates that aligning technology and pedagogy is feasible. The concept of pedagogical intent is proposed as a potentially valuable guiding principle that could enable such alignment while designing technology-mediated instruction. Designing high-quality online teacher professional development is a complex yet worthwhile endeavor. This dissertation offers valuable information about theoretical grounding related to designing online professional development, ways that productive dialogue and collaboration can be supported online, and the importance of technology-pedagogy alignment during the design process. We are only beginning to understand what works in online teacher professional development and why it works. More research is needed to identify theoretical frameworks, principles, and processes that could guide both practitioners and researchers in its design, development, implementation, and evaluation. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]