The purpose of this study was to explore how university researcher professional development design decisions built and sustained K-8 partnerships which foregrounded mathematics in integrated STEM via model-eliciting activities (MEAs). We applied a self-study methodology to facilitate a longitudinal examination of our practice in this multi-year project. We used the Decision-Making Protocol for Mathematics Coaching to understand our collaboration with division stakeholders as they worked toward integrating MEAs with district curriculum and pacing. Analysis of professional development artifacts, evidence of scholarship, and researcher memos revealed four recalibration points driven by district initiatives and leadership changes. Coaching with MEAs created opportunities for equitable student engagement and formative assessment. Implications for designing professional development that emphasizes explicit connections between the constraints of mathematics curriculum and the possibilities of teaching and learning through STEM integration are presented.