Since the advent of new technology for learning, innovative language instructors have been constantly seeking for new pedagogy to match the potential of technology-enhanced instruction. While the literature is replete with studies supporting the adoption of technologies to facilitate language teaching and learning, research into enhancing EFL learners' oral proficiency by creating an online learning community in a flipped classroom remains scanty. Therefore, the current study aimed to examine the impact of an online learning community in a flipped classroom, specifically via mobile platforms, on EFL learners' oral proficiency and their perceptions. Forty eight English-majored sophomores enrolled in two oral training classes at a four-year comprehensive university in central Taiwan were recruited to participate in this study. A mixed method was employed to analyze multiple sources of data, including pre- and post-tests on oral reading and comprehension questions, a "Community of Inquiry" (CoI) questionnaire, and the teachers' in-class observations. The flipped instruction measured by the CoI indicated that the online learning community not only facilitated meaningful and positive collaboration, but also significantly improved the participants' oral proficiency, making them feel more competent in those highly interactive learning events, such as storytelling, dialogue interaction, class discussion, and group presentations.