The present study investigates the locus of language selection in less and more proficient language learners, specifically testing differential predictions of La Heij's (2005) concept selection model (CSM) and Kroll and Stewart's (1994) revised hierarchical model (RHM). Less and more proficient English dominant learners of Spanish participated in a Stroop translation task that included semantically related and unrelated word or picture distracters. The results for the more proficient learners provide support for the CSM as well as the RHM. The results for the less proficient learners provide support for the RHM and demonstrate the continued reliance on lexical level links and the difficulty in accessing the conceptual store during second language production. The selection by proficiency model of bilingual speech production is discussed.