Using youth program models to frame the study of Gay-Straight Alliances (GSAs), we identified individual and structural predictors of greater engagement in these settings with a cross-sectional sample of 295 youth in 33 GSAs from the 2014 Massachusetts GSA Network Survey (69% LGBQ, 68% cisgender female, 68% White,M_age =16.07). Multilevel modeling results indicated that members who perceived more support/socializing from their GSA, had more LGB friends, were longer serving members, and were in GSAs with more open and respectful climates reported greater engagement. Further, there was a curvilinear association between organizational structure in the GSA and engagement: Perceptions of more structure were associated with greater engagement to a point, after which greater structure was related to less engagement.