Building on prior findings on screen time and peer interaction, this cross-national study of 260 preschoolers in Mexico City and Madrid examines how structured bilingual screen content combined with guided peer play affects vocabulary growth in a second language. Earlier research indicated that peer interaction supports early second language vocabulary more effectively than unstructured screen exposure, but it left open whether screen media designed for language learning can add value when it is coupled with, rather than substituted for, interactive play. Children aged four to five years attending public preschools in the two cities were assigned by classroom to one of three twelve-week conditions: structured bilingual screen content alone, guided peer play alone, or a combined condition in which screen episodes introduced target vocabulary that was then practised in teacher-guided peer play. English was the target language in both cities. Receptive and expressive vocabulary were assessed before and after the intervention with picture-based measures. Multilevel models showed that the combined condition produced the largest gains in both receptive and expressive vocabulary, with effect sizes of 0.62 and 0.71 relative to the screen-only condition, and that guided peer play alone outperformed screen content alone on expressive vocabulary. Gains in the combined condition were of similar magnitude in Mexico City and Madrid, despite differences in home exposure to English. The findings suggest that bilingual screen media contribute to second language development when they are embedded in interactive play, and they offer guidance for preschool programmes seeking to use media purposefully.