This thesis explores the opportunities for developing and assessing learners’ EFL oral skills in pre-vocational classrooms in the Netherlands. The thesis contains four studies. First, we evaluate the oral interaction practice offered in EFL coursebooks. In the second study, we explore ways to assess individual ability in oral interaction in a reliable and valid manner. Studies three and four report on two experimental studies. Study three investigates the effects of instructional programs on learners’ interactional ability, and study four investigates the effects of these programmes on the affective measures willingness to communicate, enjoyment and self-confidence. Additionally, this study explores the relationship between these affective variables and task achievement in oral interaction tasks. The thesis furthermore contains a summary and discussion of the main outcomes, suggestions for future research and for educational practice.