This presentation will introduce results from a longitudinal study looking at the phraseological language development of French-speaking learners of Dutch or English in two different educational settings, namely Content and Language Integrated Learning (CLIL) and traditional foreign language learning contexts (NON-CLIL). This study was carried out in the framework of a large multidisciplinary project on CLIL in Belgium and follows on from previous analyses that revealed a higher and more accurate production of phraseological units in CLIL. It is based on corpus data; informal written texts were gathered during two data collection points, the first at the beginning of the fifth year of secondary school education and the second towards the end of the sixth year. Intra-group and inter-group analyses were carried out and both the frequency and the accuracy of the learners’ phraseological lexicon were examined. Whilst SLA research often supports the fact that phraseological competence positively correlates with proficiency levels in a target language and that CLIL learners often outperform NON-CLIL ones, our study showed that high input environments do not systematically boost learners’ phraseological learning over time and that results may vary according to the foreign language.