This action research explores an effective teaching method for EFL teacher’s questioning types in a Korean online university context. By reviewing the previous studies on teachers’ questioning types which have been categorized mostly by cognitive linguistic tradition, this study sorts out the different questioning types from socio-linguistic perspective using the Systemic Functional Grammar (SFG) framework. These new categorized questioning types are applied to instruct the participant students (57) who were majoring in English and were mostly interested in TESOL (Teaching English to the Speakers of Other Languages) certificate program provided by the online university in Korea. Using a series of lecture content, two assignments, and an online discussion board, these newly added questioning types (offer and request types replacing command) were successfully taught in an online lecture entitled ‘Classroom English and Communication’ in the first semester of 2021. With a mixed analysis method, this study explains the procedures of various classroom tasks and analyzes the assignment data and online discussion board texts. This teacher classroom communication consisting of instruction and questioning needs to be reconsidered due to this study’s findings and its pedagogic implications that are clearly based on socio-linguistic perspectives.