Racial/ethnic disparities in colorectal cancer (CRC) screening and diagnostic testing present challenges to CRC prevention programs. Thus, it is important to understand how differences in CRC screening approaches between healthcare systems are associated with racial/ethnic disparities. This was a retrospective cohort study of patients aged 50-75 years who were members of the Population-based Research Optimizing Screening Through Personalized Regimens cohort from 2010 to 2012. Data on race/ethnicity, CRC screening, and diagnostic testing came from medical records. Data collection occurred in 2014 and analysis in 2015. Logistic regression models were used to calculate AORs and 95% CIs comparing completion of CRC screening between racial/ethnic groups. Analyses were stratified by healthcare system to assess differences between systems. There were 1,746,714 participants across four healthcare systems. Compared with non-Hispanic whites (whites), odds of completing CRC screening were lower for non-Hispanic blacks (blacks) in healthcare systems with high screening rates (AOR=0.86, 95% CI=0.84, 0.88) but similar between blacks and whites in systems with lower screening rates (AOR=1.01, 95% CI=0.93, 1.09). Compared with whites, American Indian/Alaskan Natives had lower odds of completing CRC screening across all healthcare systems (AOR=0.76, 95% CI=0.72, 0.81). Hispanics had similar odds of CRC screening (AOR=0.99, 95% CI=0.98, 1.00) and Asian/Pacific Islanders had higher odds of CRC screening (AOR=1.16, 95% CI=1.15, 1.18) versus whites. Racial/ethnic differences in CRC screening vary across healthcare systems, particularly for blacks, and may be more pronounced in systems with intensive CRC screening approaches.