The effects of microbial 3-phytase and glycosidase enzymes, and their interactions, on energy values and nutrient digestibility in diets rich in nonstarch polysaccharides (NSP) were studied in diets based on corn, wheat, or barley. Four diets were prepared with each cereal grain. One had no enzymes, a second had 500 units of phytase, a third had glycosidase enzyme, and a fourth had phytase and glycosidase. The glycosidases used were alpha-galactosidase (corn diet), xylanase (wheat), and beta-glucanase (barley). Glycosidase decreased intestinal viscosity, whereas phytase increased this parameter in corn diets. Phytase increased AME in corn diets, whereas beta-glucanase in barley diets improved AME and AMEn, and digestibility of dry matter, starch, beta-glucans, and lipid. Xylanase in wheat diets improved dry matter and starch digestibility. Phytase increased total phosphorus retention in all diets, and significant interactions between glycosidase enzymes and phytase were detected in wheat and barley diets. Phytase decreased phosphorus excretion in corn and barley diets, whereas alpha-galactosidase increased phosphorus excretion in corn diets. Phytase in corn diets and beta-glucanase in barley diets increased calcium retention, whereas inclusion of xylanase decreased calcium retention in wheat diets. Phytase and beta-glucanase decreased calcium excretion in corn- and barley-based diets, respectively. An interaction was detected between phytase and beta-glucanase in barley diets, in which calcium excretion was reduced. In general, no negative interactions between phytase and glycosidase enzymes were found, indicating that both types of enzymes may be used together in feeds based on corn, wheat, or barley.