We briefly present the findings from the first year of a five year long study that is examining how postsecondary mathematics students learn to use programming as a computational thinking instrument for mathematics investigations and applications. It is a naturalistic (i.e., not design-based) research that takes place in a sequence of three project-based mathematics courses (called ‘MICA’) implemented in the mathematics department at Brock University (Canada) since 2001 (Buteau, Muller, & Ralph, 2015). In this first year, we followed 6 students, in the MICA I course, as they engaged in their 4 programming-based project tasks, which account for 71% of their final grade.