Even in a unionized environment where work tasks are similar, hourly wages are identical, and tenure dictates promotions, we find that female workers earn $0.89 on the male-worker dollar (in weekly earnings). We use confidential administrative data on bus and train operators from the Massachusetts Bay Transportation Authority (MBTA) to show that the weekly earnings gap can be explained by female operators’ taking less overtime and more unpaid time off using Family Medical Leave Act (FMLA) than do male operators. We find that women value time outside of work more than men, and also have greater demand for schedule predictability and controllability. When overtime hours are scheduled three months in advance, men and women work a similar number of hours; but when those hours are offered the day before, men work nearly twice as many. When selecting work schedules, female operators avoid weekend, holiday, and split shifts more than do male operators. Women earn less in weeks with these unfavorable shifts, whereas men earn more by taking leave during the undesirable shift and substituting it with considerable overtime. Moreover, to avoid unfavorable work times, women prioritize schedule convenience over route safety, selecting routes with a higher probability of accidents. These results suggest that policies that increase schedule controllability, like shift-trading and expanded cover lists, can reduce the gender earnings gap and disproportionately increase the wellbeing of female workers.