Receptive knowledge of vocabulary has usually been the mostly investigated dimension of lexical assessment while the productive aspect of vocabulary has been studied to a lesser extent. There is hardly any research on the productive vocabulary of English foreign language learners in Turkish context, particularly as far as primary school students are concerned. Yet, it is utmost important to study learners' vocabulary levels in Turkey where English is taught as a foreign language (EFL). Within this context, this study seeks to address the effect of grade level variation in EFL productive vocabulary size of a group of young learners. In order to collect data, the participants were given a series of pictures (Heaton, 1966) and asked to create a story based on what they see in the pictures. The lexical frequency profiles (LFP) technique was used to estimate participants' productive vocabulary size with a focus on the differences and similarities among different year levels. The findings of the study present insights into developmental process of vocabulary acquisition of Turkish EFL learners.