We examine gender bias in political institutions through a novel lens: oral arguments at the US Supreme Court. We ask whether female lawyers are afforded less speaking time during oral arguments compared to male lawyers. We posit that justices, while highly educated and more aware than most of laws requiring equal treatment, may be influenced by gender schemas that result in unconscious biased treatment of male and female lawyers. Applying automated content analysis to the transcripts of 3,583 oral arguments, we find that female lawyers are interrupted earlier, allowed to speak for less time between interruptions, and subjected to more and longer speeches by the justices compared to their male counterparts. However, this pattern is reversed during oral arguments involving gender-related cases. Our most novel and significant theoretical finding is that gender negates the well-documented positive effect of being on the winning side of a case.