The aim of the study was to evaluate the supplementation of dry brewery by-products and mineral salts (Fosvimin®) in milk yield of crossbred cows in the Pucallpa area, Peru. Three groups of six cows each were used. Cows were at various phases of lactation and had various degree of crossbreeding, but with zebu predominance. The treatments were: T1 = naturalized pasture (PN), T2 = PN + 5 kg of brewery residue (Os) and T3 = PN + Os + 100 g/cow of mineral salt. The three groups of cows were confronted with the three treatments for periods of 10 days, in a randomized complete block design, where daily milk yield was recorded between days 6 and 10 of each period. Supplements of T2 and T3 were provided during milking. The available forage of the naturalized pasture was 2207.6 kg/ha of dry matter. The milk production in T1, T2 and T3 was 4.5, 4.3 and 4.8 l/cow/day respectively, showing significant difference between T3 with T2 and T1 (p<0.05). The results showed a beneficial effect of the combined supplementation of brewery's residues and mineral salts in the milk production of grazing crossbred cows.