While K-12 online learning in the United States has increased exponentially, the ability of teacher education programs to adequately prepare teachers to design, deliver, and support has been deficient. A small number of universities have begun to address this deficit through the introduction of graduate certificates in online teaching. This article examines curricular changes focused on introducing in-service teachers to K-12 online learning. This design-based research study examined changes in teacher perceptions after having completed a systematic curriculum focused on K-12 online learning, as well as track revisions to that curriculum based on the data collected. The results indicate that even in a jurisdiction where online learning has become a graduation requirement, teachers often have many misconceptions about K-12 online learning. Further, planned exposure to K-12 online learning content can have significant impact on student understanding of and interest in the design, delivery, and support of K-12 online learning.