Flipped classrooms have been widely adopted and discussed by school teachers and researchers in the past decade. However, few studies have been conducted to formally evaluate the effectiveness of flipped classrooms in terms of improving EFL students' English oral presentation, not to mention investigating factors affecting their flipped learning outcomes. In this study, an online community-based flipped learning approach was proposed for an EFL oral presentation course; moreover, a learning analytics approach was used to analyze factors affecting the students' oral presentation outcomes. An 18-week research design was implemented with the online community-based flipped classroom using Facebook as the platform for facilitating and recording peer-to-peer interactions during the flipped learning process. In addition, the students' learning performance and perceptions were collected in 3 learning stages during the 18 weeks. The experimental results reveal positive effects of the online community-based flipped instruction over the conventional video-based instruction. That is, first, the online community-based flipped instruction using mobile devices can enhance students' English oral performance. Moreover, it was found that the high improvers had a significantly higher frequency of online participation, as well as more interactive behaviors and greater satisfaction with the flipped classroom than the low improvers. These results imply that the online community flipped classroom could not only provide learning materials and out-of-class learning for students, but could also help them become more responsible and autonomous in their learning and communication. These findings could be valuable references for those who intend to conduct effective flipped classrooms with an online community to facilitate students' before-class learning participation and to improve their in-class learning performance.