Massive Online Open Courses (MOOCs) are a booming phenomenon in the digital era, having attracted millions of users around the world to date. At the same time, educational delivery via MOOCs comes with its own distinct difficulties for students and instructors, as the online nature of MOOCs creates every opportunity for digital distraction and procrastination. In this work, we consider that the digital nature of MOOCs and online learning management systems (LMSs) may also offer unique opportunities to counteract procrastination. Building on the temporal motivation theory, this study examines a number of calls-to-action (CTAs) pertaining to the completion and submission of course assignments, with an eye toward combatting student procrastination on MOOCs. We report on the results of a randomized field experiment on a leading MOOC platform in China. By randomly treating MOOC users with different CTAs related to active course assignments, we seek to examine the impacts of alternative informational interventions on students’ duration to and probability of on-time assignment submission. We consider multiple types of CTAs: a simple call-to-action, a deadline reminder, descriptive norm interventions (communicating peer assignment completion rates), and a simple CTA combined with a financial incentive. We find that descriptive norms lead to higher probabilities of assignment completion and a shorter time to completion. In contrast, we find that the deadline reminder has a surprisingly counter-productive effect. Subsequently, exploring heterogeneity in the response to our different interventions – considering factors such as course load, education level, and user tenure on the MOOC platform – we find evidence that the deadline reminder, in particular, can backfire if students’ active course load is low. This result suggests that students with low course loads may perceive the deadline to be distant, which reduces their sense of urgency and leads to complacency. We discuss the implications of our findings for both research and practice.