Phraseological phenomena—ranging from idioms to collocations to discourse organizers—have received increasing attention in second language acquisition (SLA), and examinations of such strings are characterized by two distinct perspectives on formulaic language. On the one hand, different speech acts seem to be commonly realized using certain expressions. These conventional expressions are important for the successful realization of everyday interactions and constitute an important target for second language learners. On the other, the pervasiveness of multi-word expressions has been argued to follow from the fact that such sequences are in fact stored as wholes in the lexicon, implying that they are “easier” or “faster” to process. This psycholinguistic definition of formulas is pervasive in the literature, and tests of the veracity of such a proposal have been called for; to date, little such work has been done in SLA. The current dissertation is situated against the backdrop of both of these perspectives, and draws from both in an attempt to offer insights into questions specific to each. To this end, 13 expressions identified as conventional in Pau, France were tested in an online contextualized naturalness judgment task, which was administered to 20 French natives, 20 long stay Anglophone learners of French (>1 year in Pau), and 20 short stay Anglophone learners (4-6 months in Pau). The naturalness judgments provided on this experiment revealed that all groups judged the conventional expressions similarly, whereas the reaction time results suggested that conventional expressions are mentally represented as such for both natives and nonnatives. The reaction time results are argued to be most consistent with a pragmatic competence model of conventional expression processing.