In an era where computational thinking is regarded as a basic skill for the 21st century that needs to be taught across the K-12 curriculum, research shows that teacher education programs do not adequately prepare preservice teachers to promote computational thinking skills in classroom teaching. Accordingly, the present study contributes to the body of knowledge that can be used to inform the teaching of computational thinking in teacher education through the use of scaffolded programming scripts with educational robotics activities, within the context of a science lesson about gears. The study reports effects on preservice teachers' computational thinking, knowledge about gears, and self-reported efficacy to teach with educational robotics.