The aim of this study was to evaluate the variation of the chemical composition and the performance of the oats-vetch, wheat-vetch and barley-vetch associations in various proportions of sowing in the form of hydroponic crops. The study was carried out in the city of Huancavelica, Peru, at 3690 meters above sea level. In total, 90 trays of 704 cm2 were used, with a density of 2.5 kg of seed/m2. Associations of oats/vetch (O/V), barley/ vetch (B/V) and wheat/vetch (W/V) with six proportions of grass/legume were used: 100/ 0, 80/20, 60/40, 40/60, 20/80 and 0/100. The fresh biomass production (FBP) and the chemical composition of the percentage fractions of dry matter (DM%), organic matter (OM%), neutral detergent fibre (NDF%), ethereal extract (EE%), crude protein (CP%) and total minerals (TM%) were determined. A completely randomized experimental design was used, with a factorial arrangement of 3x6 (associations x proportions) with 5 repetitions. The association, the proportion and the interaction showed significant differences (p<0.0001) on FBP (kg/m2) and chemical composition. The results show a higher FBP in B/V (6.79 k/m2), %MS in O/V (19.58%),% FDN in B/V (57.15%), EE% in O/ V (4.87%), %MM in B/V (4.19%) and %MO in W/V (95.35%). The B/V and O/V associations presented the best results in FBP and chemical composition.