The objective of this study was to evaluate the morphogenic, structural, and chemical characteristics of Brachiaria grass (Urochloa decumbens) intercropped with forage peanut (Arachis pintoi) under three-row spacings (40, 50, and 60 cm) and two post-grazing residual heights (5 and 15 cm). The experiment was performed in a randomized block design with a factorial scheme (3 x 2) with four replicates. The structural and morphogenic characteristics were considered in a factorial scheme (3 × 2) + 1 (an additional treatment of Brachiaria grass in monoculture). Chemical characteristics sampled by cutting and by hand plucking were evaluated. Brachiaria grass had the highest crude protein (CP) content at 5 cm, whereas forage peanut had the highest CP content at 15 cm in the first year, however, there was no difference in the second year. Compared to monoculture, intercropping resulted in lower final stem size, a greater number of live leaves, and increases in the following metrics: leaf elongation rate, final leaf size, and leaf life duration, most consistently with 5 cm residual height in the second year. The forage peanut improved the morphogenic and structural characteristics of Brachiaria grass primarily when managed at 5 cm post-grazing height, regardless of row spacing.