The present study aimed to evaluate the protein quality of oats. Winter oats (n=35) and spring oats (n=36) were assayed for protein content and amino acid composition. Essential amino acid index (EAAI) was also used to evaluate the protein quality. Beside the chemical procedures a digestibility trial was carried out to compare the amino acid (AA) digestibilities of oat containing diets and the oats varieties. In the frame of the trial the effect of using glucanase enzyme was also tested. Both winter oats and sprig oats containing higher amount of essential amino acids compared with maize or wheat. The protein quality of oats, expressed in the form of EAAI was also about 10% higher than the other cereal grains. Incorporating oats into broiler diets at 20 and 40 % surprisingly improved the AA digestibility of the diets. The positive effect of oats were AA dependent. Only slight positive glucanase effects were found. The enzyme effect was also AA dependent. The linear regression procedure was used to calculate the true ileal AA digestibilities of the oat grains. These results showed, that the measured AA digestibility coefficients of oats are lower than the table values and also lower than those of maize and wheat.