The numerous studies of parliamentary oversight and institutional design have largely ignored the ability of parliamentary opposition to strengthen and utilize mechanisms of parliamentary oversight by which they can challenge incumbents. This article explores the evolution of oversight mechanisms in Norway during 1970-96, and the ways new mechanisms have been utilized by the opposition to penetrate the policy-making world of public bureaucracy. An analysis of two cases investigated by the new Standing Committee on Scrutiny and Constitutional Affairs in 1994 and 1995 reveals that opposition members imposed institutional constraints on the incumbents. That in turn produced a move away from the traditional fixed control system, and towards a shifting-focus control mode. In addition, the strategic creation of oversight arrangements appears to offer incumbents very little control over the evolution of oversight arrangements. Some control, however, may be exercised over the conclusion of oversight cases due to the leadership's ability, through the use of selective incentives, to persuade parties to join the government in the final vote in the Committee.