Despite widespread recognition of the importance of computer science (CS) education and an increased focus on computational thinking (CT) instruction in the U.S., there remains a significant shortage of qualified K-12 CS teachers. Preparing preservice teachers to teach CS is essential for ensuring a sustainable future for CS education. This experience report presents a CT/CS module initiative designed to prepare secondary preservice science and math teachers to teach CT/CS through an instructional methods course that integrates instructional practice within an elementary after-school program. This initiative employs the preservice teacher preparation framework (Mason & Rich, 2019) that includes the observe-practice-reflect cycle. Within this framework, the preservice teachers began with incorporating unplugged lessons and then transitioned to robotics to teach CT/CS concepts. In this experience report, we detail the design and implementation of this CT/CS module initiative and share findings that revealed the preservice teachers’ increased confidence, adaptations in lesson planning, and the challenges faced in teaching CT/CS. These takeaways aim to inspire and inform other teacher educators and practitioners working to prepare the next generation of CS teachers.