Lexis was, for a long time, paid scant attention to in foreign language teaching. Over the last 20 years, however, vocabulary acquisition has become a focus of academic research. In particular, the Cognitive Linguistic perspective on foreign language learning offers a rich theoretical framework for research in this area, since it encapsulates both ease of learning and a more profound knowledge of the target language. Learning vocabulary in school contexts, however, is still strongly associated with rote learning in many parts of the world, that is, the repetition of items, usually using lists with little or no contextual information. The implications of Cognitive Linguistics form the basis of an intervention study carried out in German primary schools. This investigates whether lessons enabling learners to elaborate on words and thereby process the vocabulary more deeply lead to better long-term retention of these items. The results of this empirical study are used to evaluate the relevance and benefits of the theoretical implications of vocabulary research for primary school learners of English.