In 2000, Congress passed the Breast and Cervical Cancer Prevention and Treatment Act (BCCPTA) to provide coverage through Medicaid to women who screened positive for breast and cervical cancer. We aimed to determine if late-stage breast cancer prevalence decreased among Oklahoma women after passage of BCCPTA. Data were obtained from the Oklahoma Central Cancer Registry during 2000-2011. We estimated prevalence proportion ratios (PPR) using modified Poisson regression between the proportion of women with late-stage breast cancer and timing of diagnosis related to BCCPTA. Among uninsured women, the probability of being diagnosed with late-stage cancer after enactment of the BCCPTA was 0.80 (95% CI: 0.67, 0.96) times the probability before enactment. This was significant among uninsured women living in metro counties (PPR: 0.74, 95% CI: 0.61, 0.90) but not in non-metro counties (PPR: 1.05, 95% CI: 0.71, 1.56). These findings may be similar to other rural states with large uninsured populations.