This article reports on the outcomes of a longitudinal case study to gauge the impact of content and language integrated learning (CLIL) on two of the least researched language skills: oral comprehension and production. It worked with 24 students in the fourth grade of Compulsory Secondary Education in a public school in Andalusia (southern Spain) over the course of a year and a half in order to measure the impact of CLIL on oral comprehension and production skills after a one-year intervention programme (post-test) and to determine whether its effects pervade after a six-month period (second post-test), when these same students are in Baccalaureate. The results reveal that, contrary to what has traditionally been sustained in bilingual education, it was productive, as opposed to receptive, oral skills which were more positively affected by CLIL in the medium- and long term. The outcomes also provide interesting data on what aspects of oral competence are particularly amenable to being taught through CLIL (e.g. more cognitively complex listening activities) and which need to be developed over a longer time span in order to be significantly improved (e.g. pronunciation and fluency).