This action research study presents the findings of using a formative assessment strategy in an online mathematic course during the world-wide outbreak of COVID-19 at the University of Passau, Germany. The main goals of this study were: (1) to enhance students' self-regulated learning by shifting the direction of assessment from instructors to the students; and (2) to promote deep active learning in mathematics. Students were required to conduct self-regulated learning on a selected topic. They were encouraged to formulate two multiple-choice questions (MCQs) and pose them after each presentation in an online course. The effectiveness of Student-generated Questions (SGQs) as a learning strategy was measured in terms of: (1) students' engagement; and (2) learning outcomes. While evidence on students' engagement was gathered through an online questionnaire survey, the learning outcomes were measured by analyzing the quality of SGQs. Results indicated that authoring questions, though leading to a higher students' engagement with the materials, could be quite challenging for students and did not lead to higher achievement. The authors provide some suggestions for improving the process through regular uses of digital technologies such as PeerWise.