There has been an exponential growth in Language Massive Open Online Courses (LMOOCs) in the past decade. LMOOCs have also become an emergent and topical area of research in CALL, in particular, vis-a-vis learners' perceptions and experiences. However, not much attention has been paid to analysing the features of LMOOCs. We argue that a systematic investigation of LMOOC design features is vital, especially in light of recent criticisms by some CALL and language education scholars regarding the incompatibility between LMOOC designs and language teaching and learning theories and methodologies. This systematic review, which employs Hall's (2013) framework of web-based instruction, addresses this gap by analysing instructional and assessment features of 100 LMOOCs on "edX" and "Coursera." The synthesised findings suggest three strengths of LMOOCs: Most LMOOCs are introductory, suitable for beginning language learners ("directionality"). Most are easy to navigate because of their "consistency" in format and features. And most employ a range of multimodal instructional materials ("multimodality"). Three limitations are also identified: There are few opportunities for instructor-learner and learner-learner interaction ("interactivity") and learner-centred, formative assessments ("accountability"). Besides, LMOOCs are designed with a prescribed learning sequence without addressing individual learner differences ("adaptability"). Based on our analysis, practical suggestions for LMOOC developers are discussed. 2013 edX Coursera directionality consistency multimodality interactivity accountability adaptability.