Teachers navigate ongoing accountability pressures that target writing in each content area, yet little is understood about their experiences with or their rationales for integrating writing into content area lessons. While previous research describes writing in U.S. secondary classrooms and explains barriers to writing integration, this study investigates teacher decision making to determine why teachers in various content areas are integrating writing. Using a multicase study design, we explored teacher reflections to discern the reasons why teachers chose to integrate writing frequently. Four teachers, one from each primary content area (mathematics, English language arts, science, social studies), reflected on their writing integration over one quarter. Findings revealed that teachers who integrate writing frequently value the substantial benefits of regular writing for their students. Teachers saw that frequent writing led to students both producing written products more independently and deepening their disciplinary understandings. Teachers also saw benefits to their own pedagogy; specifically, they better understood students' learning processes and planned more attentively. This research suggests that committing to frequent writing integration can (1) enhance students' writing and disciplinary knowledge, and (2) enrich teacher knowledge related to supporting students' writing practices and using writing as a tool for learning in the content areas. Our findings also highlight the complex relationship between teacher beliefs and teacher practice. By looking at the instructional decision making of teachers who integrate writing frequently, we offer guidance on how pre-and in-service teachers might use reflection in and on action to develop a commitment to writing instruction.