Explicit vocabulary instruction is widely practiced in Taiwanese language classrooms, yet limited attention has been given to how learners can acquire vocabulary incidentally through authentic online reading. While both explicit and incidental learning are recognised as complementary processes in second language vocabulary acquisition, research on how incidental vocabulary learning occurs in digital contexts remains limited. In this study, incidental vocabulary learning is defined as the unintentional acquisition of new words that takes place as a by-product of meaning-focused reading, rather than through deliberate vocabulary study. This study aimed to develop an English reading course for Taiwanese undergraduates, utilising online consumer electronics reviews to promote incidental vocabulary learning. The study was organised into three stages. In Stage One, a corpus-based analysis was conducted, involving the creation and examination of a corpus of online consumer electronics reviews to generate a word list that later served as the basis for a vocabulary test. Stage Two encompassed a 12-week classroom investigation employing mixed methods in action research. This approach monitored learners through spirals of ‘planning, acting, observation, and reflection’ (Lewin, 1946), ensuring active reading involvement to investigate incidental vocabulary learning. A quasi-experimental design was used to assess students’ vocabulary gains. Stage Three examined students’ perceptions and experiences through focus group interviews. Quantitative findings indicated that students were able to acquire vocabulary incidentally through extensive online reading, while qualitative insights highlighted themes related to their experiences and strategies for handling unfamiliar words. This study provides an alternative approach to enhance students’ vocabulary acquisition and increase their reading motivation.