While there is a substantial body of research on the role of glosses in fostering reading comprehension and vocabulary acquisition, the findings on relative efficacy of first language (L1) and second language (L2) glosses are conflicting. This study investigates the impact of Farsi (L1) and English (L2) paper-based glosses on bilingual English as a foreign language (EFL) learners' vocabulary retention and recall. During a two-month treatment, the participants read the passages under L1 gloss, L2 gloss, and control conditions. Following the treatment, a vocabulary post-test and a month later, a delayed post-test were administered to gauge any vocabulary gains. Results showed the superiority of L1 over L2 glosses in the retention test (post-test). The delayed post-test scores revealed a roughly similar performance of both experimental groups. Pedagogical implications for L2 teaching/learning were discussed.
