Given the increasing awareness of oral communication in this era of globalized collaborative learning trends, there is an imminent need to inform language educators of ways in which the under-researched oral interactional strategies are related to first language (L1) teaching. However, no consensus has yet been reached on the relationship between interactional strategy use and oral language proficiency. This study investigates the effect of oral interactional strategy use on group discussion performance in L1 Chinese for Primary 5 students (N = 140) in Hong Kong. Based on ANOVA and regression analyses of the data on group discussion performance, five strategies have been identified: expressing actively, asking for opinion, expressing attitude, giving clarification and non-verbal language. They all significantly predicted students’ group discussion performance, with overall strategies explaining 55.5% of total variation of the performance, where higher-proficiency students tended to use more strategies that enable comprehension and elaboration in the group discussions. The patterns of strategy use among students with different levels of discussion performance have also been identified. Implications of the findings are discussed with reference to the roles individuals play in the overall performance of group discussion. Copyright © 2019 Walter de Gruyter GmbH, Berlin/Boston.