Since 2011 the growth in Massive Open Online Courses (MOOCs) has been so enormous that, according to the Economist magazine, “the ivory towers of academia have been shaken to their foundations” (2013). One proposed benefit of MOOCs is that they allow considerable flexibility in organizing learning. At the same time, there is evidence that learning is associated with conscientiousness (O’Connor and Paunonen, 2007), especially planning, self-discipline and organization. This may be even more important in flexible courses than in traditional learning.This study explored the impact of conscientious behavior in a MOOC on student completion.Data from 27,993 students on a course was analyzed (including only those who watched at least one lecture and/or submitted at least one assignment). Students engaging with the course at roughly the same time every week were regarded as showing planning and self-discipline (high conscientiousness) and an index of regularity was developed. The association of this regularity with course completion was assessed. The results showed a moderately strong and highly significant association (chi-square = 1205.4 (5), p < .001), Cramer's V = .324. This suggests the flexibility of MOOCs may be of most benefit to those with conscientious study practices. The development of tools which help students to plan and develop conscientious practices may well aid student completion and learning in MOOCs.