Pebble counts were performed to assess the bed surface grain size distribution at five delineated mussel habitats in the Big River, Missouri. These data were collected in support of research assessing the mussel communities and characteristics of freshwater mussel habitats in the Big River (Albers and others, 2016; Roberts and others, 2016). Pebble counts were performed at the mussel habitats following the methods of Wolman (1954). Grain diameters of 99-100 particles were measured on the intermediate axis. The pebble count data are semi-continuous; grains smaller than 2 mm were classified as sand, and grains larger than 64 mm were classified as either cobble (65-256 mm) or boulder (greater than 256 mm) but measured lengths were not recorded. This dataset has been published previously in categorical format by Albers and others (2016) and Roberts and others (2016).