The uneven effects of EU membership conditionality on Eastern European reforms continue to puzzle the research community. Sometimes, the research focus has been too large, considering EU membership conditionality as a policy implemented uniformly across policy areas. Other efforts take a too narrow approach by trying to explain the effects of EU membership conditionality in single sectors. I suggest studying this phenomenon through a set of mid-level theories in a cross-country, cross-sectorial approach. I argue that both the intensity of EU membership conditionality and reform outcomes are contingent upon the policy sector context; hence, we should take a sectorial contextual approach in studying them. Reform outcomes result from the interplay between EU’s and domestic leaders’ interests in a particular sectorial reform. I assume domestic leaders to be rational, power driven actors. I argue that, since they act in some weakly institutionalized political environments such as Eastern European societies, they represent the principal actors in the power game. I assume the EU to be a rational actor as well; yet, differently from Eastern Europe, the role of individual leaders is less distinguishable in the highly institutionalized EU political theatre. In this case, EU institutions are the primary political agents. They are interested in maintaining and enlarging the Union as a stable democracy. Expanding an earlier argument that views the EU as established through consociational practices, I argue that EU membership conditionality is a tool to impose institutional reforms in the EU aspirant countries, so their institutions can be receptive to the EU consociational practices once they join the Union. In these countries, the consociational character of conditionality is more visible, since it seeks to impose in aspirant countries the same practices that have brought democratic stability in some member states. The EU does not impose consociational practices on unified societies, but simply seeks to make their institutions receptive to the EU consociational practices. I test these arguments with the cases of institutional reforms in postcommunist Albanian and Macedonia. I conclude that, generally, EU membership manages to change Eastern European leaders’ interests in institutional reforms, but when it cannot, the reforms are almost impossible.