SUMMARY:Nutritional constraints of rearing calves on native grasslands during their first winter is a common problem in Uruguay due to insufficient quality and quantity of forage. Winter supplementation on beef cattle grazing native grasslands using grains or their by-products has been studied before, but little attention has been given to restricting the access of animals to an adjacent enhanced forage basis, such as oats forage. Thirty-six castrated Hereford calves grazing native grasslands during their first winter were randomly allotted to one of the following treatments:(a) Everyday (E), with access to an adjacent oats forage crop for 4 hours a day (28 hours/week); (b) Monday-through-Friday (MthF), with access to the same crop for 5 hours 36 min per day (28 hours/week); (c) Control (C), where animals did not have any access to oats. The experiment was separated in two Phases:Phase I where treatments were applied (winter), and Phase II, after the treatments were applied (spring), to evaluate eventual carry-over effects. Restricted grazing on oats affected herbage mass and sward height of native grasslands in both experimental phases (P