The Tiwanaku civilization (around AD 500–1100) originated in the Bolivian altiplano of the south-central Andes and established agrarian colonies (AD 600–1100) in the Peruvian coastal valleys. Current dietary investigations at Tiwanaku colonial sites focus on maize, a coastal valley cultivar with ritual and political significance. Here, we examine Tiwanaku provincial foodways and ask to what degree the Tiwanaku settlers maintained their culinary and agrarian traditions as they migrated into the lower-altitude coastal valleys to farm the land. We analyze archaeobotanical remains from the Tiwanaku site of Cerro San Antonio (600 m asl) in the Locumba Valley and compare them to data from the Tiwanaku site in the altiplano and the Rio Muerto site in the Moquegua Valley during the period of state expansion. Our findings show high proportions of wild, weedy, and domesticated Amaranthaceae cultivars, suggesting that Tiwanaku colonists grew traditional high-valley (2,000–3,000 m asl) and altiplano (3,000–4,000 m asl) foods on the lowland frontier because of their established cultural dietary preferences and Amaranthaceae's ability to adapt to various agroclimatic and edaphic conditions.