Despite significant investment in colorectal cancer (CRC) screening, 40% of US adults are not up-to-date. Commitment devices, which are psychologically tailored approaches to enforce health goals, may be an effective method to increase CRC screening. Compare the effectiveness of a commitment device (patient self-ordering fecal immunochemical test (FIT) kits) to standard CRC screening outreach. A retrospective observational study. Participants were > 49years and < 75years, had no history of CRC, and were eligible for CRC screening. An electronic screening reminder with an embedded order button allowed participants to order FIT kits directly from a patient portal. Those who used the order button were promptly sent a kit; those who did not were later mailed kits. Primary outcome was completion of FIT kits. Secondary outcomes included number of days to completion, completion of follow-up for positive results, and CRC diagnosis; we also examined prior use of FIT kit. We used inverse probability of treatment weights to control for pretreatment imbalances. The cohort comprised 176,231 participants: 53% female; median age was 59; 11% were Asian, 21% Hispanic/Latino, 7% black, 51% White, 3% other/mixed race. Approximately 10% (N = 16,918) used the button. Using inverse probability of treatment weights, we found that those who used the button had 3.8 times the odds of completing a kit compared to participants who did not (odds ratio, 3.77; 95% confidence interval, 3.57-3.98). Within the button group, 63% of those eligible completed a FIT kit in the year prior to the button compared to 87% in the year after the button became available (p < 0.0001). The ability to self-order screening kits may act as a commitment device that increases CRC screening. Scalable tools leveraging existing patient portals such as this can complement existing CRC outreach strategies.