Simply defined, effective English Language Arts (ELA) instruction is cohesive, integrated, and requires students to think deeply. Creating such instruction is difficult, however, because of insufficient training in instructional planning and the numerous types of curricula teachers must navigate that may not align well. Therefore, new secondary ELA teachers could benefit from high quality professional development focused on effective ELA planning practices. In this case study, a group of five secondary ELA teachers from different schools worked together with an expert facilitator to test the effectiveness of a professional learning community (PLC) model of professional development, a form that demonstrated promise for effective professional development. Using qualitative methods, this study determined (a) the instructional planning needs of new ELA teachers (b) how the PLC impacted teachers' planning for cohesive, integrated, and deeply thoughtful instruction, and (c) what strengths and weaknesses existed in the design of this online training environment. Findings suggest that teachers have instructional planning needs across the domains of cohesion, integration, and content depth that teachers can improve within a PLC of this kind. Teachers most often improved in their understanding of between unit cohesion as well as wherever they had preintervention interests. However, the teachers' growth was limited, overall, suggesting training of this kind should occur over longer than five weeks and/or with a different disbursement of the content. Implications include that even when preservice and in-service supports exist to assist new teachers with instructional planning, teachers will likely need professional development for instructional planning because of the highly contextualized and nuanced nature of the topics studied. In addition, PLCs seem to offer a viable way to offer assistance to new ELA teachers in improving their instructional planning. However, the limited nature of available research using this professional development model suggests that continued research should occur. This study's strengths and weaknesses in content and design may help others to fill in some of the gaps of PLC design options in future iterations of instructional planning PLCs that use technology-based platforms for collaboration. [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.]