This study critically examines the factors contributing to verbal participation and the achievement of desired learning outcomes in English medium instruction (EMI) classes in a Korean higher education institution. This case study uses mixed research methods including surveys, focus group interviews and peer observations of students and professors of selected EMI classes. This paper has highlighted several factors which influence active verbal participation and the achievement of desired learning outcomes in EMI classes. The research provides a rich understanding of how differences in teaching styles and learning activities significantly affect levels of verbal participation in EMI classes. The findings suggest that in order to achieve desired EMI learning outcomes, it is necessary to examine all of the interconnected elements within the education system, including students, professors, the teaching context, as well as the institutional systems at national and international levels. This research has raised a number of challenges and criticisms concerning EMI courses including the effectiveness of learning of subject content via a foreign language.