English Medium Instruction (EMI) research has mushroomed in response to the rapid increase in EMI courses in higher education (HE) worldwide. Despite concerns about the need for EMI teacher professional development (PD) there are few studies on PD in EMI. We present a study of EMI teacher PD which adopted a model of equal status collaborative research between a language specialist and two EMI teachers whereby the latter were presented with highly detailed analyses of their lessons over a period without evaluative commentary/feedback from the language specialist. Our findings suggest that the two teachers reacted enthusiastically to the model but one teacher felt a greater need to move towards an interactive pedagogy than the other. Possible explanations are given and suggestions for adapting future research are made.