This article discusses a study on how language use and language development can be promoted through engaging students in different participation roles in board games. Theoretically, the study is grounded in sociocultural perspectives of activity theory and the role of play as a form of human motivation. A group of Grade 4 primary students learning English as a second language in Hong Kong participated in the games, with alternating roles as players and facilitators. Students' discursive and embodied participation in the games was analysed to reveal how changing participation roles constitute a form of social-relational mediation that motivates students' deployment of different interaction practices and multimodal semiotic resources to achieve context-sensitive, object-related and goal-directed actions in collaborative group activities. The data also show students' agency and self-regulation when they enacted the same participation role with different subject positions and semiotic resources. This article concludes by calling for more attention to how engaged participation resulting in situated purposeful language use can be promoted through different forms of participation in social activities such as board games.