Monolingual and parallel concordancers have both been found to benefit second-language (L2) grammatical development. However, the relative benefits of these two concordancer types remains unclear. The present study compares learning outcomes and learners' perceptions of a monolingual English (Corpus of Contemporary American English, COCA) and a French-English parallel concordancer (Tradooit), using verb-preposition collocations as a target feature. Students in an advanced English as a second language (ESL) course completed three concordancing activities where they used either Tradooit (for French L1 speakers) or COCA (for other L1s) to formulate rules for challenging verb-preposition collocations (e.g. "arrive in/at"). Pre- and post-tests showed significant learning gains for both groups, which were maintained in delayed post-tests; however, perception questionnaires showed that Tradooit was perceived as easier and more useful for language learning. We suggest that these differences may be due to the type of cognitive work involved in L1-L2 comparison versus L2 pattern-finding, but that these two processes may both lead to noticing and learning. [For the complete volume of short papers, see ED590612.]