Abstract: Research-based best practices that employ learning theories such as Project-Based Learning have not been thoroughly developed for the constraints of the K-12 online setting, nor have they been tested in this unique context. K-12 online teacher-developers face many constraints during the process of instructional design, and require additional supports to translate these learning theories into their lessons. The researchers of this study employed a design and development research method to co-develop three project-based lessons for a 9th grade literature course online. Resulting from documentation of a repetitive instructional design process, the researchers propose two models, the Project-Based Online Lesson Structure Model, which maps an order of content presentation to offer to learners, and the Project-Based Online Learning Instructional Design Model, which maps a step-by-step process for teacher-developers to follow in designing project-based online lessons for K-12 learners.