An essential component for assessing the accuracy and fluency of language learners is understanding how mode of communication and task type affect performance in second-language (L2) acquisition. This study investigates how text-based synchronous computer-mediated communication (SCMC) and face-to-face (F2F) oral interaction can influence the performance of language learners in producing grammatical forms accurately when learners of English as a second language complete different tasks in their L2. Findings show a systematic variability in learner interlanguage that depends on mode of communication and task type. L2 learners used articles more correctly and produced advanced-stage questions more frequently in text-based SCMC than in F2F. These findings suggest that task types and the mode of communication in which a task is completed need careful selection based on pedagogical purposes in order to maximize L2 learning and better evaluate L2 performance.