Cornmeal snacks containing blends of soy protein isolate (SPI) with cotton linter cellulose (CEL) or soy cotyledon fiber (SF) were produced with a twin screw extruder. SPI increased expansion and reduced collet bulk density. Samples containing soy materials were darker than those containing 10% CEL or only cornmeal. CEL reduced expansion and increased residual moisture. The effects of SF were intermediate between those of SPI and CEL. Samples containing either type fiber had slight increases in nitrogen solubility and higher losses of available lysine after extrusion. A sensory evaluation panel found samples with 15% SPI and 10% either fiber were tan and soft, with a nutty or grain flavor.