This research project seeks to gauge the autonomous power of the European Commission within the Open Method of Coordination (OMC), a new mode of governance coined at the Lisbon European Council in March 2000 and based on the principle of the voluntary cooperation of Member States. Two cases form the basis of this inquiry, namely, quality in work, a policy issue addressed under the banner of the European Employment Strategy, and child poverty and social exclusion, a key item on the agenda of the OMC for Social Inclusion. A primary impetus at the heart of this project is one of ontological pluralism. Rejecting a zero-sum interpretation of the rationalist/constructivist debate, this study constitutes a plea for a conversation across paradigms. The domain-of-application model employed here works by preserving the integrity of individual theories while specifying a particular scope condition under which constructivist and rationalist insights are likely to prevail. Selecting two cases on the basis of the critical scope condition of issue sensitivity, a central postulate informing this integrative research design is that high issue sensitivity (quality in work) invites strategic interaction among pre-constituted social actors driven by a behavioural logic of utility-maximization, while low issue sensitivity (child poverty and social exclusion) allows for a fundamentally norm-guided behaviour. Concretely, in effecting this theoretical dialogue, two sets of causal hypotheses are examined. On the one hand, rational choice institutionalism (principal-agent theory) offers a number of suppositions about the Commission’s institutional power, that is, its ability to transform the conditions of action of self-seeking national governments. On the other hand, sociological institutionalism conceptualizes the Commission’s productive power (i.e. its power to constitute the interests and identities of individual agents) through the lens of discourse analysis. Testing theoretical predictions against collected data makes plain the superior explanatory value of independent variables and causal mechanisms of rationalist lineage in capturing the essence of the Commission’s autonomous power in the case of quality in work and the congruity of sociological institutionalism’s original conjectures in the area of child poverty and social exclusion. Crucially, this strict correspondence corroborates the pertinence of the critical scope condition of issue sensitivity in delineating the explanatory ambit of both theories and attests to the co-existence of different forms of autonomous power wielded by the Commission within the framework of the OMC.