The present research examined the extent to which the initial approach to a research-writing course by STEM and non-STEM second-language learners may entail the contribution of different dispositions to course performance and ultimately be responsible for dissimilar outcomes. Individual differences in dispositions and behavior were assessed during the first four weeks of the semester. They pertained to an understudied college population of young women from a society (Saudi Arabia) that has only recently begun to address gender inequalities in education and the workforce by placing women at the center stage of its economic development. There were no differences in generic and research-specific writing skills, but performance on the first assignment was higher in non-STEM students, whereas general confidence (i.e., self-efficacy) and confidence specific to research writing were higher in STEM students. Nevertheless, STEM students were more likely to complete the course successfully than non-STEM students. It was concluded that the former treated initial poor performance as a warning call to increase engagement, thereby independently addressing their own difficulties. Instead, the latter required additional instruction and counseling as engagement by itself was insufficient to lead to academic success. These findings underscore the relevance of targeted, evidence-driven interventions that acknowledge the different academic needs of STEM and non-STEM students.