The importance of professional development (PD) is clearly understood; however, little is known about how the most effective PD influences teachers' learning and how teachers perceive PD that goes beyond the typical two-hour session on an aspect of instruction. In this article, the authors present the response of a group of middle school teachers to a university-led, eight-week curriculum intervention study that served as a form of PD for the teachers. In this study, researchers from a university and a non-profit educational research organization conducted a vocabulary intervention study at four middle schools in New England. Part of a federally funded intervention study, this initiative focused on the academic vocabulary learning of Spanish-speaking English language learners (ELLs). The teachers were first presented the curriculum during a 12-hour training session and were coached for eight weeks throughout the implementation of the curriculum in their classrooms. The original intent of the intervention training and coaching was to promote fidelity of implementation of the curriculum, not to research the effects of the intervention training as professional development for teachers. However, as the intervention progressed, the teachers often expressed to researchers and coaches that they were learning new aspects of vocabulary development and instruction. Therefore, during final interviews conducted following the completion of the intervention, teachers were asked to talk about their perceptions of the intervention as a PD opportunity. The findings reported in this article are based on these final teacher interviews. The findings presented here suggest that using university-school partnerships through curricular interventions can serve as valuable opportunities to provide effective PD, because these types of interventions allow for both content/instructional learning as well as sustained support. The article begins with a summary of what is known about effective professional development, continues with a description of the intervention, and concludes with a focus on the teachers' experiences in working collaboratively with the researchers as a form of professional development.