This study involved a pilot implementation of an evidence based school readiness intervention in new community contexts. The Head Start Research Based, Developmentally Informed (REDI) program was implemented in preschools on and near a Native American reservation with both indigenous and non-indigenous students and teachers. The REDI curriculum involved 5 subcomponents targeting children's literacy skills and social-emotional development. Teachers were provided with inperson and on-line training and in-person implementation support from a REDI coach. Implementation fidelity included ratings of of curriculum dosage and child engagement, as well as coach ratings of teaching quality using a modified version of the Classroom Assessment Scoring Scale (CLASS). Teachers indicated which adaptations they made to the curriculum and the reasons for these adaptations. Teachers also completed qualitative, post-implementation interviews to obtain their impressions of REDI and the need for planned modifications in their context. Analyses included measures of implementation fidelity and qualitative evaluation of adaptations. Results indicated that teachers found the REDI program both feasible and helpful for their students. Suggestions for planned adaptations included more STEM activities and the freedom to choose the dialogic reading books. Many spontaneous adaptations were noted. Teachers indicated that pragmatic issues, such as lack of time, were the main reasons for adapting the program, and deletions and substitutions of curricular activities were the most common types of changes. Implementation of program subcomponents improved gradually over the course of the school year. Some subcomponents were more likely to be adapted than others.