Computational thinking and activity are becoming an increasingly important aspect of what it means to conduct scientific and mathematical work. In light of this, there is a need for STEM education studies that examine the ways in which students engage with computational tools as they reason about scientific and mathematical concepts. In this talk, I review relevant literature on computational thinking in STEM and make a case for an increasing focus on computing in STEM education research. As an example of computational thinking and activity, I present results from a study in which undergraduate novice programmers engaged with tasks designed to use basic Python programming to teach particular combinatorial ideas. I highlight noteworthy aspects of students’ experiences with using computation in a mathematical context. I conclude by framing this work within ongoing efforts to better understand the nature of computational thinking and activity for undergraduate STEM students.