The aim of the study was to measure differences in nutritive content, over four seasons, of native grasses such as Aristida purpurea Nutt. var. longiseta (Steud.) Vasey, Bouteloua curtipendula (Gould et Kapadia), Bouteloua hirsuta Lag., Bouteloua trífida (Thurber), Chloris verticillata Nutt., Digitaria insularis (L.), Panicum halli (Vasey.), Setaria grisebachii (Fourn.), Setaria macrostachya (H.B.K), Tridens eragrostoides, Tridens muticus (Torr.) Wash., and cultivated Cenchrus ciliaris (L.) and Rhynchelytrum repens (Willd.) C. E. Hubb. that are used as forages for grazing ruminants. Cenchrus ciliaris was included as reference grass of good nutritional quality. Higher chemical content and EDDM and EDCP occurred during the wet seasons (summer and autumn). Because of their good nutritional quality, grasses such as Panicum hallii, Setaria grisebachii, Setaria macrostachya and Tridens eragrostoides can be considered good forages for ruminants.