Independent regulatory agency has become the standard institutional choice in Western Europe. Little is known, however, about the involvement of legislators in their design and in their monitoring. In this paper, we analyse ex-ante and ex-post legislative involvement for 48 regulatory agencies enacted in France. We show that legislators debate and design more substantially agencies for which the government bill has already granted them more powers to appoint members to their board, or to be appointed as board members themselves. Once enacted, agencies that allow greater participation by legislators in their decision-making are subject to greater scrutiny, and this even after controlling for routine oversight activities. Regulatory domains matter, though only for ex-post legislative oversight. These results suggest that legislative involvement is selective and driven by strategic considerations. More fundamentally, they imply that legislative involvement could be more important in regulatory agency activities than usually assumed.