We analyze the interaction between university professors’ teaching quality and their research and administrative activities. Our sample is a high-quality individual panel data set from a medium size public Spanish university. Although, researchers teach roughly 20% more than non-researchers, their teaching quality is also 20% higher. Over much of the relevant range, we find a nonlinear and positive effect of research output and teaching quantity on teaching quality. Instructors with no research are 5 times more likely than the rest to be among the worst teachers and up to two-thirds of the professors could improve their teaching by increasing research.