This study provides a novel approach for testing the universality of perceptual biases by looking at speech processing in simultaneous bilingual adults learning two languages that support the maintenance of this bias to different degrees. Specifically, we investigated the Iambic/Trochaic Law, an assumed universal grouping bias, in simultaneous French–German bilinguals, presenting them with streams of syllables varying in intensity, duration or neither and asking them whether they perceived them as strong-weak or weak-strong groupings. Results showed robust, consistent grouping preferences. A comparison to monolinguals from previous studies revealed that they pattern with German-speaking monolinguals, and differ from French-speaking monolinguals. The distribution of simultaneous bilinguals' individual performance was best explained by a model fitting a unimodal (not bimodal) distribution, failing to support two subgroups of language dominance. Moreover, neither language experience nor language context predicted their performance. These findings suggest a special role for universal biases in simultaneous bilinguals.