English learners (ELs) make up a significant portion of the nation’s K-12 student population who come from culturally and linguistically diverse backgrounds. ELs bring a wealth of diversity to the United States’ education system; however, teachers’ limited knowledge and practices that integrate ELs’ cultural, linguistic, and prior educational experiences in the general education curriculum can contribute to low academic growth and overidentification of ELs into special education programs, particularly for learning disabilities in reading. This study examined the impact of online professional development on general and special education teachers’ knowledge of data-based individualization (DBI) and curriculum-based measurement (CBM) to adapt validated reading interventions with culturally and linguistically responsive practices (CLRPs) for ELs with persistent reading difficulties. Results of this single-case, multiple probe across participants study indicated an increase in knowledge of DBI and CBM to adapt validated reading interventions with CLRPs; however, a functional relation was not established due to the study ending before all the teachers could complete the professional development components. The findings of this study provide several implications for online DBI professional development and adapting validated reading interventions for ELs. Suggestions for future research are also offered.