Firms increasingly rely on suppliers to perform tasks in new product development (NPD). Research has only recently begun to focus on the processes to manage this supplier development responsibility, and has hardly investigated how firms collect and analyze information regarding the cost and performance of alternative supplier offerings. Our study addresses this gap, through a field survey among 144 paired samples of project leaders and cost analysts involved in the same NPD projects. On the basis of literature and qualitative research, we conceptualize a substantive model. We first use a substantive validity assessment to vet the measures for the proposed constructs. We then test the substantive model with structural equation modeling using a multiple-sample analysis. The results strongly show that monetary quantification of differences and detail gathering play significant roles in successfully leveraging supplier development responsibility. The findings support the hypothesis that the extent of development responsibility that suppliers have leads the development team to a more focused monetary quantification of the differences in alternative supplier offerings. Monetary quantification of differences has a significant, positive effect on the extent of supporting-detail gathering and on the development speed of the project, whereas supporting-detail gathering has a significant, positive effect on the product advantage of the new product as well as development speed. These findings are robust across the two functional perspectives. Our study complements the literature on interfirm control and monitoring by demonstrating the effects of selective and focused output controls.