The aim of this study was to evaluate the effect of controlling the intensity of grassland grazing (Campos biome), through control of herbage allowance (HA), on mass of internal organs of beef cows of different genotype. Mature beef cows (n = 32) were used in a randomized complete block design with a factorial arrangement of herbage allowance (2.5 vs. 4 kg DM/d; LO vs. HI) of native pastures (52% DM, 8.4% crude protein, 39.7% acid detergent fiber,) and cow genotype (CG; pure breed: Angus-Hereford vs. F1 reciprocal crosses; PU vs. CR). The experiment was conducted for 3 years and at the end of the third year at 192 ± 10 d postpartum cows were slaughtered and weight of all tissues and organs were collected. Means from a mixed model with repeated measure analysis were considered to differ when P ≤ 0.05. The gastrointestinal tract (GIT) mass (kg) was greater (P = 0.02) and the diaphragm and lungs mass tended (P ≤ 0.09) to be greater in HI that LO cows, while liver and heart mass were greater (P ≤ 0.01) in CR than PU cows. Absolute kidney mass was not affected by HA or CG. However, when expressed as a proportion of the carcass, GIT and kidney weights tended to be lower (P < 0.08) and diaphragm weight was lower (P = 0.04) in CR than PU cows (151.6 vs. 161.1 ± 4.0; 8.2 vs. 8.9 ± 0.3 and 12.4 vs. 13.3 ± 0.3 g/kg carcass for GIT, kidney and diaphragm, respectively). In addition, relative weights of heart and kidney were lower (P ≤ 0.05) in HI than LO cows (8.2 vs. 8.9 ± 0.2 and 8.1 vs. 9.0 ± 0.3 g/kg carcass for heart and kidney, respectively). Neither absolute nor relative head weights differed between cow groups. Absolute weight of the skin tended (P = 0.08) to be greater and relative weight was greater (P = 0.01) in LO than HI cows (30.3 vs. 32.3 ± 1.0 g/kg carcass). Although absolute weight of legs was not affected by HA or CG, its relative weight was 16.7% less in CR than PU and 14.8% less in HI than LO cows. Results suggest that LO and PU cows could have increased maintenance energy requirements through increased relative organ weights, which could affect cow-calf system productivity.