There is a need for higher quality professional development for writing teachers (Cutler & Graham, 2008; Gilbert & Graham, 2010; Kiuhara, Graham, & Hawken, 2009). Even though writing is an essential skill, quality writing instruction for students and the professional development for writing teachers is lacking (National Commission on Writing, 2003; Cutler & Graham, 2008). Thus, the purpose of this qualitative collective case study was to document the language and classroom practice of three teachers when professional learning was related to writing process and situated in a Professional Learning Community (PLC) framework. Guiding my inquiry were the following research questions: 1) How is professional learning around writing process evidenced in teachers' language? 2) How is professional learning around writing process evidenced in teachers' classroom instruction? Data were collected though observations, interviews, and artifacts. Data analysis involved both deductive and inductive coding, pattern coding, and thematic analysis (Miles, Huberman, & Saldana, 2014). Three themes emerged when exploring teacher professional learning as evidenced by their language and classroom instruction: improvement in pedagogical content knowledge, development in knowledge-"of"-practice, and growth in reflective practice. Findings reveal that professional learning that is connected throughout a unit of study, driven by a team's own agenda, situated in classroom practice, and surrounded by the analysis of student work positively influences teachers' language and practice around writing instruction. These findings confirm much of the research on professional learning communities but adds a new perspective on the possibilities with not only writing teachers, but teachers of poetry writing. These findings are step forward to emphasizing the need for even more professional learning opportunities and training for writing teachers. [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.]