This study compares the relative effectiveness of reading and writing sentences for the incidental acquisition of new vocabulary in a second language. It also examines if recall varies according to the concreteness of target words. Participants were 203 French-speaking intermediate and advanced English as second language (ESL) learners, tested for incidental acquisition of 16 rare concrete, or abstract L2 words. Immediate and delayed cued recall was used to assess acquisition. Results from immediate recall show superior recall for writing tasks over reading tasks, and for concrete words over abstract words. However, delayed recall scores suggest that this superiority disappears over time.