This article describes the effects of participation and collaboration in an in-service professional development project for secondary content area teachers referred to as "turnaround training." The participating teachers were experienced, skilled practitioners in their content areas (math, science, social studies, or English language arts) who were challenged with meeting the needs of students who were learning English as well as course content. The goal of the professional development project was to improve student performance by enhancing the skills of the secondary teachers. The authors found that the training project enhanced the technical skills of participants for working with English language learners. Furthermore, these newly minted English as a second language (ESL) "experts" negotiated their professional identities as they translated what they learned about multicultural competence, second language acquisition, and teaching ESL into turnaround training sessions for their colleagues. (Contains 1 figure.)