This study examines the effect of 'length of stay' on the written and oral development of two groups of Spanish-speaking students learning English in the UK through the Erasmus Program. Written and oral data were collected from 46 participants by means of a composition and an oral narrative after stays of two months (25 students) or three months abroad (21 students) in the target language country. The learners' written and oral samples were analyzed in terms of fluency, accuracy, lexical richness and complexity. The results of the statistical analyses suggest that there are no significant differences in the gains made by the two groups of learners; therefore, an additional month abroad may not be long enough to produce significant differences in learners' second language development in terms of the measures of written and oral production considered in this study.