The online flipped classroom has become increasingly applied to provide students with active learning. This search aimed to investigate the effectiveness of video lectures in an online flipped learning on students' learning outcomes, students' video evaluation, and their experience in an online flipped classroom. This study employed mixed-method research implementing a quasi-experimental design using quantitative and qualitative data collection: pre-test and post-test, a questionnaire and interview. The participants were 78 Indonesian undergraduate students taking English as a foreign language (EFL) content course at one of the universities in Indonesia. The findings revealed that the students' learning outcomes in the flipped classroom outperformed those in the control group. The students' evaluation of the video lectures was high, and their evaluation was consistent with how they positively perceived the video lectures in the flipped classroom. This investigation showed the roles of video lectures on the students' participation and active learning in the flipped classroom during Coronavirus disease (COVID-19) pandemic time.