We report on a longitudinal case study (n = 9) about popularization writing skills in undergraduate interdisciplinary students. Writing skills were determined by analyzing components of the cognitive process model of writing proposed by Hayes. Keystroke logging and video observation were used to analyze the text construction process (the process level) in third-year writing. Genre knowledge (the control level) was analyzed through text analysis and assessment of first-year and third-year texts. Results showed that writing was highly individualized at the process level, including switches between processes, timing, number of edits, and reliance on the source text. At the control level, popularization genre knowledge did not significantly change over time and text quality remained low to average, suggesting a lack in genre knowledge. Choices in the writing process are, thus, not reflected in the quality of the writing product. These findings point to a need for explicit training in popularization discourse alongside academic discourse training.