This paper extends the literature on the consequences of over-education, in particular quit outcomes. It is the first study that explicitly tests the impact of job satisfaction and on-the-job training for workers in educational mismatched jobs and on quit behavior using a longitudinal data set. Accounting for unobserved heterogeneity and endogeneity, the dynamic analytical framework examines labor market outcomes for job-mismatched workers. We find that over-education alone, or accompanied by skill under-utilization in combination with lower job satisfaction, increases the incidences of job quitting. Opportunities for training facilitate the retention of initially job-mismatched workers. These results have implications for interpreting mismatch data, retention, and resource allocation.