Writing professional learning is often overlooked amidst public-school system demands, which include scarce funding and competing state mandates and priorities (Tooley and Connally, 2016). In addition, writing teachers are often subject to professional learning experiences that are directed by others rather than being tailored to their own needs (Hicks et al., 2018). In this study, an elementary English Language Arts supervisor examined a different approach to professional learning that empowered teachers to design their own inquiry learning experiences in collaboration with their colleagues while also building their capacity as instructional leaders in the process. Grounded in inquiry learning (Dewey, 1938; Schon,1992) and community of practice (Wenger, 1998) theories, this study explored how pre-kindergarten through 5th grade elementary writing teachers in a small Mid-Atlantic US school district co-designed inquiry professional learning, and how their English Language Arts supervisor supported their teacher leadership in the process. Data collected included questionnaire responses, transcriptions of audio-recorded pre- and post-interviews and eight collaborative professional learning sessions, field notes, artifacts/documents from professional learning sessions, as well as researcher reflections and analytic memos. Study findings highlight opportunities for further inquiry-based professional learning about writing instruction and shifts to existing professional learning structures to empower and support teachers as professionals and as instructional leaders. Recommendations for future research include more research to provide insights on the role of curriculum supervisors in facilitating inquiry-based professional learning and to examine how schools can build capacity via teacher leaders. [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.]