The main purpose of this study is to investigate the factors for success and course completion through the lens of participants in a Massive Open Online Courses (MOOCs) system implemented in Turkey. Thirty-two participants were selected on the basis of purposive sampling among 5000 enrolled users from 10 MOOCs, who were then classified into 3 types --lurking, moderately active, memorably active-- based on their participation rate in the course activities. The data were collected via the use of two semi-structured interviews. According to the findings, the factors for success in MOOCs to the participants were divided into three categories: instructor effectiveness, course design, and personal factors. As to the factors for course completion, the categories identified were the instructor, course design, personal factors, technical issues, and affordability/clarity. The findings regarding success and course completion were discussed in detail and recommendations were provided to enhance participation in MOOCs.