Annual production of native grasses on the Texas Coastal Prairie was decreased by 90, 66, and 67 kg/ha in 1978, 1979, and 1981, respectively, for each 1% increase in mixed-brush canopy cover in the range, from 12 to 57%. Differences in regression coefficients among years were not significant (P$0.05), although rainfall varied from 84% of the 26-yr average (91.5 cm) in 1978 to 150% of the annual average in 1981. Grass production during the growing season (May through October) only was decreased by 58, 113, and 78 kg/ha in 1978, 1979, and 1981, respectively, for each unit percentage increase in brush canopy cover. A greater proportion of the annual rainfall occurred during the growing season of 1979 than during the drier spring and summer of 1978. Native grasses typical of brush-free Coastal Prairie occupy the interstitial areas among the mixed-brush mottes, but bunch cutgrass (Leersia monandra Swartz) is the only grass that persists from the canopy edge to 1.5 m inward from the brush driplines. Little or no herbaceous vegetation grows in the centers of the mottes.