the composition of perennial forage peanut (arachis pintoi 'belmonte') was evaluated at different ages (64, 82, 112 and 142 days) of forage harvesting in a complete randomized blocks design with 4 replications. there was a linear decrease (r2= 0.91) of crude protein levels from 23.55 to 19.1 %, at 64 and 142 days respectively. there were linear increases for neutral and acid detergent fibers and cellulose levels with increase of harvest age. no differences were observed in total tannin (20.2), total phenol (31.8) and condensed tannins (15.7) in equivalent g/kg dm with increase in age. perennial peanut has high crude protein level, and adequate fiber content, as well. the tannins contents were not modified by age and anti-nutritional factors presented acceptable levels.