In recent years, the European Union (EU) has intensified its anti-subsidy actions against China. Now, it is prepared to target transnational subsidies granted by countries to their investors in other countries. In the two glass-fiber cases, the European Commission takes new approaches to expand the oversight of foreign subsidies, going significantly beyond its established practice. The new approach signals the EU’s tougher stance in the actions against subsidized imports from third countries. It demonstrates the Commission’s wider ambitions to broaden the scope of its existing toolbox when it comes to tackling the negative impact of Chinese subsidies in the European economy. This article seeks to answer the question of to what extent the oversight of foreign subsidies will be permissible in anti-subsidy investigations against third countries.