We present the results of interdisciplinary bioarchaeological research on the multicultural frontier context of the (Re)conquest of Islamic Iberia, focusing on human and animal subsistence as a proxy of political, social and economic changes from multiple sites in the province of Guadalajara between 10th and 15th c. CE.Guadalajara, located in central Spain was defined by opposing Christian and Muslim frontier societies in the 11th and 12th centuries. We study sites dating to either side of the (Re)conquest to explore this frontier in transition, including the castle of Molina de Aragón, Prao de los Judíos, the Cathedral of Sigüenza, Alcázar Real de Guadalajara, Palacio de los Guzmán, castle of Zorita de los Canes, the cemetery of Guadalajara and the Campus de las Cristinas cemetery. These are mainly urban and military settlements which played a role as central places in the region and represent differing religious communities, including Muslim, Christian and Jewish contexts.Biomolecular techniques were applied to these contexts in order to obtain a deeper understanding of animal husbandry strategies and food consumption patterns by both livestock and humans. Bulk carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) stable isotope analyses were performed on the bone collagen of >300 samples, including humans, domestic mammals, birds and fish. A subsample of these were also analysed for oxygen (δ16O) and strontium (87/86Sr) isotopes to investigate mobility. Research questions to be addressed through these data include exploring differences in production strategies through time and between religious communities, differences between food supply networks to cities and castles and the consequences of changes in political rulership in animal husbandry management. Particular themes emerge, such as the use of C4 plants as fodder or the supply and consumption of fish at these inland settlements.