While understanding of domain specific vocabularies is essential in content learning, little research informs teaching practices for glossary learning. This study examines the relationship among vocabulary learning, student autonomy, and course performance through the theoretical framework of self-determination theory and second language acquisition. Undergraduate business law students (n = 209) took weekly online glossary quizzes via a learning management system before coming to the class. Students were divided into two groups where (a) glossary quizzes were required and graded and (b) optional and not graded. There was a significant relationship among the number of quiz attempts and overall course performance. While both groups valued the glossary quiz as a helpful learning activity, students in the required group made more attempts at quizzes (t = 17.029, p < 0.01), received higher scores (t = 2.841, p < 0.01), and demonstrated higher perceived competence (t = 5.544, p < 0.01) in their command of vocabularies than students in the optional group. Also, students who reported more autonomous motivation toward the course made more attempts and received higher scores. Findings suggest required glossary quizzes enhance student engagement with quizzes and further improves content learning. However, the use of glossary quizzes proved effective only when students actually completed these numerous times. Educators are recommended to encourage repeated attempts at glossary quizzes where unfamiliar vocabularies are crucial to content understanding and professional practice.