A considerable amount of current research on teaching and teacher education focuses on teacher collaboration. Teacher collaboration is presumed to be a powerful learning environment for teachers' professional development. However, empirical research about how teachers actually learn in collaborative settings is lacking. In this study, learning activities were explored in relation to reported changes in cognition and/or behaviour of six teachers that participated in collaborative groups. These six teachers were interviewed after group meetings and also asked to report learning experiences in a digital logbook six times during a period of one year. Qualitative analyses of both data sources resulted in seven configurations of (successions of) learning activities and reported changes in cognition and/or behaviour. A closer look at these configurations showed that (successions of) learning activities in collaborative settings resulted mostly in reported changes in cognition. These reported changes in cognition often concerned confirmation of own ideas or teaching methods. The high number of confirmations of own ideas or teaching methods may be explained by the reform context in which these teachers work. Teachers who are experimenting with new teaching methods can feel insecure about these newly acquired methods and, therefore, seek confirmation from their colleagues. (Contains 1 figure, 4 tables and 1 note.)