Political actors are often assigned roles requiring them to enforce rules without giving in-groups special treatment. But are such institutional roles likely to be successful? Here, I exploit a special case of exogenously assigned intergroup relations: debates in the Danish Parliament, in which Parliament chairmen drawn from parliamentary parties enforce speaking time. Analyzing 5,756 speeches scraped from online transcripts, I provide evidence that speech lengths are biased in favor of the presiding chairman’s party. On average, speakers of the same party as the presiding chairman give 5 percent longer speeches and are 5 percent more likely to exceed the speaking time limit. The paper contributes to the extant literature by demonstrating political intergroup bias in a natural setting, suggesting that group loyalties can supersede institutional obligations even in a "least likely" context of clear rules, complete observability, and a tradition of parliamentary cooperation.