This article analyzes the evolution of the oversight function in the Congress of Deputies between 1979—the start of the First Legislature—and May 2026, through an empirical study of oral questions raised in plenary sessions and interpellations submitted during each legislature. The hypothesis posits that accountability in Spain has undergone a functional transformation: although the regulatory framework has remained largely unchanged since 1978 and oversight is employed more frequently, it has been progressively hollowed out, giving way to a logic of political communication aimed at polarized electorates. The analysis identifies four phases: a foundational stage closely aligned with the constitutional function (1979–1986); the consolidation of the two-party system and the mediatization of oversight (1989–2004); a fracture of the electorate into incompatible audiences due to multilevel competition and the crisis (2008–2016); and a denaturalization marked by polarization, coalition governments, and the dilution of political accountability (2016–present). The results show that the numerical increase coexists with a loss of corrective capacity.