The efficacy of diets containing 40%-50% wheat, barley, or oat grains, fermented by a solid-state fermentation process, on bird performance, carcass yield, digestive organ development, and intestinal viscosity was tested. Compared with broiler chicks fed unfermented grains, those fed fermented oats had increased feed intake, and treatment with fermented wheat and barley improved the feed conversion ratio at days 21 and 42. Treatment with fermented barley and oats resulted in increased body weight at day 42. Treatment with fermented wheat and oats increased the percentage of carcass yield. Birds fed unfermented grains had highly viscous digesta, not seen among birds fed fermented grains. Compared with those fed unfermented grains, birds fed fermented grains had reduced (P < 0.05) size and weight of the digestive tract, but increased liver weight. In conclusion, feeding broiler chicks diets of fermented grains, particularly wheat and barley, yielded certain performance and carcass benefits, promising a growth-stimulating effect.