As previously reported, mastery learning has been used by the author to provide instruction to more than 750 students in a total of 24 separate offerings of five different semester-long courses. In prior publications, the results of anonymous student feedback collected at the end of the semester have been reported, including: quantitative results of Likert-scale responses to five common questions; and representative comments to open-ended questions. These prior results suggest that at least two responses are predominant, namely: 1) rejection of mastery learning as "unfamiliar"/"unfair", or "lazy on the part of the professor"; or 2) welcoming of mastery learning as "empowering", or "an opportunity for self-ownership of learning on the part of the student". To improve our understanding of the attitudes of students towards mastery learning, a qualitative approach was employed in the current study. Through discussions with experts in qualitative methods, a structured interview guide was constructed by the author and included questions about: 1) "Seven Principles for Good Practice in Undergraduate Education"; 2) "Principles of Adult Learning"; and 3) ABET student outcomes. The structured interview guide also included an opportunity for free response to open-ended queries about flipped classroom, blended delivery, modified mastery learning, and flexible summative assessment. Experts in qualitative methods recommended an initial pilot study with a population of ten students. These ten alumni were selected from a subpopulation of the 750 students who previously completed at least one course employing mastery learning. The subpopulation was identified as individuals who earned a grade of "A" in a course with mastery learning and subsequently completed a semester-long course of "Independent research" with the author. The subpopulation included approximately 50 individuals students. Ten random individuals were selected from this subpopulation, contacted via email and follow-up telephone call, and invited to voluntarily participate in a one-on-one structured interview with the author. The interviews were transcribed and analyzed for themes by two individuals. The summary results of thematic analysis from these structured interviews are reported as a preliminary pilot study. In brief, these ten alumni provided a favorable view of mastery learning, and the results of this pilot study suggest that the structured interview guide is an appropriate starting-point for a more robust qualitative study employing a more formal approach such as interpretative phenomenological analysis or narrative discourse analysis.