Based on Biggs’s “3P Model”(Presage Process Product),this study conducted a questionnaire survey among 692 university blended foreign language learners. Using structural equation modeling (SEM), the study investigated the mechanism by which task value and peer support (presage factors) influence satisfaction (learning outcome) with MOOC based blended foreign language learning through learning engagement and knowledge sharing (process factors). The findings indicate: (1) Both task value and peer support significantly positively predict learning engagement, knowledge sharing, and learning satisfaction. (2)Learning engagement and knowledge sharing both played a partial mediating role between task value, peer support, and learning satisfaction. More importantly, the study revealed a chain mediating effect in the path from “task value / peer support → learning engagement →knowledge sharing → learning satisfaction,” indicating that learning presage factors and learning process elements jointly influence learning satisfaction. The dual mediating mechanism of learning engagement and knowledge sharing highlights the positive effects of affective cognitive engagement and collaborative knowledge construction on learning outcomes.