Scholars have long bemoaned congressional disinterest in oversight. We explain varied congressional attention to oversight by advancing the contingent oversight theory. We show how the structure of congressional committees, partisan majorities, and theories of delegation together explain when, why, and for how long Congress investigated executive branch malfeasance between 1947 and 2004. Divided government, partisan committees, and committees characterized by broad statutory discretion generate more investigations, whereas distributive committees and unified government dampen Congress’ investigatory vigor. The conduct of oversight depends on more than a desire to produce good government or the incentive structures faced by individual members of Congress.