Màster de Lingüística Aplicada i Adquisició de Llengües en Contextos Multilingües, Departament de Filologia Anglesa i Alemanya, Universitat de Barcelona, Curs: 2014, Turors: Roger Gilabert i María Luz Celaya.The purpose of the study reported in the present article is to explore whether differences in second language proficiency and working memory capacity affect the grammatical complexity of second language oral performance. Data from a film retelling task were used to analyze the oral grammatical complexity of a group of 91 L1 Catalan/Spanish learners of L2 English from the GRAL group corpus. Syntactic complexity and grammatical variety measures were employed for the analysis. In order to account for text length differences in the narratives, the square root of the denominator was used rather than the denominator itself. Results suggest that, when using this operationalization, both syntactic complexity and grammatical variety measures end up being positively correlated with L2 proficiency. On the other hand, no relationship was found between any of the employed measures and working memory capacity. The results are discussed in the light of previous research on the relationship between second language grammatical complexity and both proficiency and working memory capacity.