Advent of internet has a revolutionary impact on every sector of economy and so is with the education sector, which has witnessed the evolution of online education through scalable educational technology, namely, Massive Open Online Courses (MOOCs). The purpose of this paper is to summarize the pool of available knowledge related to MOOCs in the scholarly literature, published during the period 2013-2020. One hundred and two available published studies in peer reviewed journals & conferences searched in major academic databases have been reviewed and presented in the systematic literature review. The findings have been divided under the various research themes of MOOCs including geographical contribution of MOOC studies, citation trends, prominent research themes, theoretical frameworks and methodological rigor in the existing scholarly works. The results demonstrate that most empirical research were conducted by the researchers having affiliation to institutions based out of United States followed by institutions in the developing economies of China and India. The most focused area of research in MOOCs is on MOOC adoption. Limited research has happened on poor MOOC completion status, the instructor-related topics and on democratization of MOOC. Thrust areas of MOOC researches and future research directions are also discussed.