Using a structural equation modeling approach, this study investigates the structural relationships between second language (L2) oral proficiency and interest in learning the target language (L2 interest), in the presence of potential mediating variables (i.e. perceived importance of speaking, out-of-class contact with L2 resources). It also examines if interactive and noninteractive out-of-class L2 contact function differently in the structural model. Data were collected from 1,922 college students taking Chinese, French, Russian, and Spanish language classes in the United States. Key findings suggest that (1) L2 interest, as one measure of integrativeness and intrinsic motivation, strongly drives L2 oral development. However, its effect is completely mediated by the perceived importance of speaking; (2) Out-of-class L2 contact, either interactive or noninteractive, significantly correlates with L2 interest but has no significant effect on L2 oral proficiency; (3) however, interactive and noninteractive out-of-class L2 contact still function differently in the structural relationship. Interactive language practice based on digital tools could play a promising role in future L2 learning. Pedagogical implications are presented in the discussion section.