Online and blended learning (OBL) brings unique advantages to K-12 teachers and students. Thus, it is essential to prepare preservice teachers (PSTs) for designing effective K-12 OBL lessons in educator preparation programs (EPPs) so they can utilize OBL's distinctive characteristics to benefit their students immediately when they have their own classrooms. The purpose of this research is to introduce the design and implementation of this topic, K-12 OBL, into the stand-alone edtech course for middle grades PSTs. This study investigates PSTs' self-reported beliefs, technological pedagogical content knowledge (TPACK) development, and lesson design scores. Results demonstrated that PSTs developed positive beliefs and some TPACK domains. The majority of PSTs designed blended lessons and demonstrated mastery in instructional materials, learning activities, and learner interactions, but needed to improve learning objectives, assessment and measurement, and accessibility and usability. PSTs developed positive beliefs and TPACK domains similarly despite the course modalities. Nevertheless, PSTs enrolled in the blended section had higher lesson design scores compared to their peers in the online section. Challenges, such as lack of time, depth, and content-specific knowledge, exist that prevent some preservice teachers from designing more effective lessons. The researcher argues that a technology infusion method should be used to prepare PSTs for OBL in EPPs. Practical strategies for integrating new topics into the edtech course are shared. Directions for future research on the effectiveness, challenges, and productive possibilities of coaching preservice teachers to design effective K-12 OBL lessons are also discussed.