As the popularity of online courses in higher education keeps increasing, the importance of student engagement gets highlighted. In an online learning environment, peer interaction gets emphasised when students work in small groups in breakout rooms. In this case study, qualitative content analysis and discourse analysis were used to analyse breakout room recordings (458 min in total) of two small groups in a 14-week synchronous online language course. The study focused on how engagement at small group level seems to emerge from the group's interaction, which is a primordial site for language learning, and what kind of collaborative engagement practices seem to support it. The findings suggest that affective, behavioural, and cognitive engagement often co-occur and that they may either support or hinder each other. Also, the group members may be engaged in diverse ways at the same time. Three collaborative engagement practices were identified: participation in group discussions, making and negotiating proposals, and collaborative writing. Participation in group discussions highlighted the importance of both verbal and nonverbal communication and the importance of equity in participation. When making proposals, the role of tentativeness was emphasised as that seemed to open space for interaction in the small group. Finally, collaborative writing was found to engage students specifically from the language learning perspective. The findings suggest that small group interaction and collaboration play a key role in group level engagement. It is suggested that small group level should be taken into consideration when operationalising the concept of engagement in online learning environments.