The use of forage plants adapted to dryland regions in the feeding of small ruminants is a fundamental strategy to ensure the sustainability of the production system, contributing to the food stability of herds even in periods of water scarcity. We hypothesized that the use of Cnidoscolus quercifolius as a substitute for buffel grass, both in the form of hay, in the diet of sheep increases the intake of dry matter and crude protein, leading to greater daily weight gains and carcass yield. The aim of this study was to evaluate the inclusion of Cnidoscolus quercifolius hay as a replacement for buffel grass hay in sheep diets, on intake, digestibility, performance, ingestive behavior, and carcass yield. Thirty-two uncastrated male crossbred Dorper sheep (150 days of age, 19 +/- 0.35 kg (mean +/- SD) initial body weight) were distributed in a completely randomized design with 4 treatments and 8 animals per treatment. The treatments consisted of 4 diets containing different levels of Cnidoscolus quercifolius hay (0, 33.33, 66.66, and 100%) replacing buffel grass hay. The experiment lasted 76 days. Replacing buffel grass hay with Cnidoscolus quercifolius hay in the diets reduced the intake of ether extract and the digestibility coefficients of dry matter, crude protein, ether extract, neutral and acid detergent fiber, and nonfibrous carbohydrates (p < 0.05) and increased the intake of neutral detergent-insoluble nitrogen and the chewing time per ruminal cuds (p < 0.05). A quadratic effect was observed for daily and total weight gain and feeding and idling times (p < 0.05). Under the experimental conditions, although dry matter intake remained similar, the use of Cnidoscolus quercifolius hay as a replacement for buffel grass hay is recommended at levels up to 66.66% in sheep diets, as it promotes higher daily and total weight gains.