In this longitudinal study, we examined teachers' self-efficacy as a long-term predictor of their mastery goal orientation and three dimensions of instructional quality: supportive classroom climate, effective classroom management, and cognitive activation. Mastery goal orientation was also analyzed as a predictor of instructional quality. Teachers' optimism, engagement, and strain were assessed to gain information about the construct validity of the scales on self-efficacy and mastery goal orientation. We analyzed the self-report data of 203 German in-service teachers who participated in all of three time points of assessment (the years 2001, 2008, and 2011). Confirmatory factor analyses supported the assumed three-dimensionality of instructional quality. Teacher self-efficacy was found to be relatively stable and to be a long-term predictor of instructional quality as indicated by the results of latent variable modeling. Moreover, instructional quality is predicted by mastery goal orientation, which in turn is regressed on self-efficacy. As supported also by bias-corrected bootstrapping, mastery goal orientation partially mediated the relationship between classroom climate and self-efficacy. Results and an outlook for future research are discussed.