The COVID-19 pandemic has notably increased the use of distance education, particularly in Türkiye's higher education English courses. Even after the normalisation process, compulsory English courses in Türkiye, the learners of which receive education in English for general purposes, are still being taught via distance education. Such a practice could well be implemented with a massive open online course (MOOC), called a language MOOC (LMOOC). To this end, the current study focused on the development, implementation, and evaluation of a General English Language MOOC (GELMOOC) designed according to the syllabi of Turkish universities. With 2957 participants enrolled, the course's effectiveness was assessed through a single group pretest-posttest design, employing a quasi-experimental study. Accordingly, learners' language achievement levels were assessed prior to and after the GELMOOC treatment. Then, a learner satisfaction survey was also administered post-course. Results showed significant improvements in English proficiency and high satisfaction with the course's content, design, and delivery. The findings highlight the potential of and areas for improvement in LMOOCs in the literature and the foreign language teaching context.