ABSTRACT.- In Uruguay, methane (CH4) emitted from livestock sector contributes with 46.1 % of the total national emissions, where more than 70% of the beef finishing cattle are fed with forage varying the quantity or quality offered. As CH4 emissions are affected by quantity and quality of food intake, there is a need to quantify these changes. This work aimed to quantify the effect of different NDF content of forage diets on CH4 emissions from beef steers during the finishing stage.