One way to assess the quality of education in post-secondary institutions is through the use of performance indicators. Studies that have compared currently popular process indicators (e.g., library size, percentage of faculty with PhD) found that after controlling for incoming student ability, these process indicators tend to be weakly associated with student outcomes (Pascarella and Terenzini, 2005). In addition, while much research has found that students increase their critical thinking skills as a result of attending college, little is known about what goes on during the college experience that contributes to this. The purpose of this research was to examine the validity of higher-order questions on tests and assignments as a process indicator by comparing it with gains in critical thinking skills among college students as an outcome indicator. The present research consisted of three studies that used different designs, samples, and instruments. Overall, it was found that frequency of higher-order questions can be a valid process indicator as it is related to gains in students' critical thinking skills.