This study was made on the Rancho Claro Farm, municipality of Doradas (Caldas). The aim was to determine the effects of cutting age on forage production and the nutritional quality of marvel grass (Dichanthium annulatum) for hay production. The study was made in previously chosen grassland; 21 100 m2 plots were included, and the cutting ages were set at random (40; 50; 60; 70; 80; 90, and 100 days). The treatments were arranged in a completely randomized design with three replications, the age effect on production and quality was analyzed through variance analysis and the Tukey´s test. Regression analysis and the Pearson test were made to determine correlation. Forage production was observed to vary between 5.8 and 23.6 t ha1 of FM. The highest protein value was observed on the 40th day (7.9 %), with values above 5 % on the 70th day. The dry matter (DM) percent and neutral detergent fiber (NDF) increased with age; the highest contents were observed after 80 days. The crude energy (CE) values were similar in all the ages. Quality decreased as age advanced, but forage production increased. It was concluded that forage production and quality can be determined at any age, provided the height and forage production per m2 are known at initial growth stages.