This multiple case study sought to examine preservice computer science teachers' beliefs, motivational orientations, and teaching practices, as currently, they remain to be adequately researched. Eight participants were selected via maximum variation sampling for this study of trainee teachers during their first practicums in Turkey. Trainee teachers were observed in the natural setting of a computer science classroom during their teaching try-outs. Interviews were conducted with them on either side of their pre-planned lessons. Results show that teacher efficacy, self-efficacy related to using and integrating technology, and classroom management influenced participants' teaching practices. Further research is necessary to examine the consistencies and contradictions between preservice CS teachers' beliefs and practices and how these change during field experience and exemplify good practice for the benefit of CS education.