Objective supplementation of forage with grain requires knowledge of (1) forage quality, and (2) the depression in forage intake due to grain feeding. Four ‘Suwannee’ bermudagrass [Cynodon dactylon (L.) Pers.] hays of 4-, 6-, 8- and 10-week regrowth were fed ad libitum with and without limited grain to sheep. The amount of grain offered in each hay-grain diet was restricted such that it provided an estimated 50% of the total digestible energy (DE) intake. Determination of this amount of grain was based upon: (1) predicted DE intakes of hays when fed alone, and (2) expected replacement rates (kilocalories of hay DE intake depression per kilocalorie of grain DE consumed). When hays were fed alone, gross energy (GE) intake decreased (P<.05) with advancing maturity from 4- to 6-weeks and from 8- to 10-weeks regrowth. When incorporated in hay-grain diets, however, there were no differences (P>.05) among hays in GE intake. Digestibility of hay GE was depressed (P<.05) by grain feeding in all but the 10-week hay. All hay-grain diets had higher (P<.05) GE digestibilities and DE intakes than the comparable hays when fed alone. Depression of hay DE intake due to grain was greatest with the highest-quality hay and least with the lowest-quality hay. Consequently, the greatest increase in total DE intake was achieved by supplementing the lowest-quality hay.