This study examines the feasibility of an AI-enhanced professional development programme designed to support EFL secondary teachers in bilingual course development in Taiwan. Employing action research methodology, the programme was implemented across six in-service teacher cohorts (N=137), with training duration varying between six hours (n=62) and two hours (n=75). The training framework incorporated lesson planning, assessment design, and evaluation measures, utilizing a Padlet platform that provided structured AI tool prompts and exemplar materials for arts and music courses. Data collection comprised group-based bilingual lesson planning products, overall survey, and researcher reflective journals. Preliminary findings suggest the programme's potential feasibility, with participants successfully completing group-based bilingual course designs despite limited prior experience with AI-enhanced pedagogy. Participants demonstrated considerable willingness to incorporate this approach in their future individualized planning. Training duration emerged as a crucial variable, with six-hour implementations generating more comprehensive outputs than two-hour ones. The study identifies several contributory conditions: online delivery mode, optimal class sizing, and structured AI prompt guidance. These insights may inform future professional development initiatives within the EFL context of approaching bilingual education. Additionally, the findings suggest promising potential for leveraging AI-enhanced course design to tackle obstacles in bilingual lesson planning.