Querns and millstones were central to the Roman agricultural economy, but are still relatively poorly understood. Using an exceptionally detailed dataset from the Roman town of Silchester as its main case study, this paper explores the supply of querns and the supply of flour in Romano-British urban sites and their rural hinterlands. The first part of the paper focuses on the assemblage of 715 querns and millstones from Silchester as commodities in their own right. It describes the stone types used for querns in the region, how the use of these changed over time, within and outside the town, and how the supply of querns to the town differed to that of the hinterland. These patterns of exploitation are used to make inferences about social and economic behaviour. Querns and millstones are also evidence for the preparation of flour and can be used to help us understand food-supply mechanisms, especially when considered together with archaeobotanical evidence. Analysis of the querns and millstones from closely dated contexts demonstrates that use of hand-powered rotary querns peaked in the town during the latest Iron Age and earliest Roman period. The use of rotary querns decreased significantly thereafter until, by the third century, the use of hand-operated rotary querns within the town was probably confined to a very basic household level in a domestic setting. At the same time, during the second or third century, powered millstones were introduced, with the archaeobotanical evidence suggesting a mill at an out-of-town location. Analysis of querns and millstones from a 20 km hinterland around Silchester suggests that household-level grinding was common, but that centralised milling was operating at a very low level and only to the north-west of the town. It is suggested that some flour was produced at centralised locations further afield and brought into the town ready ground. Supplementary material is available online (https://doi.org/10.1017/S0068113X21000040) and comprises detailed information on the lithologies of the querns and millstones from Silchester (including photographs), publication details of the sites in the town's hinterland and a spreadsheet recording the material.