This qualitative study, through the lens of Bloom's revised taxonomy, investigates adult learners' self-generated quiz activity on their online learning in a graduate-level course offered in 3 semesters. The quiz activity aimed to engage students to think about their learning goals while actively interacting with the learning content and performing from an instructor's perspective with the assessment tools they created. Furthermore, completing the activity was also intended to support the learners in the online class and evaluate their learning performance. Findings show that the quiz activity promotes learners' active learning and motivates them to think and use questions for assessing their peers' learning. Self-generated quizzes enhance learners' engagement with the learning content and improve their cognitive processes to gain knowledge. Findings also indicate that adult learners benefit from creating an assessment tool as practical skills in online learning for their future career and current work settings as educators.