Implantation with anabolic steroids can improve weight gain of beef cattle on endophyte-infected (E+) tall fescue (Lolium arundinacea), but the effect has not been determined over a range of stocking rates. A 2-yr grazing experiment evaluated combinations of four stocking rates (3.0, 4.0, 5.0, and 6.0 steers/ha) and implantation treatments (with or without) for yearling steers grazed on E+ ‘KY-31' tall fescue. At the conclusion of grazing in the second yr (22 June), steers were placed on a bermudagrass [Cynodon dactylon (L.) Pers.] pasture and rectal temperature and serum prolactin were monitored for 8 d to assess recovery from toxicosis-related heat stress. There was an implantation x stocking rate interaction (P < 0.05) on ADG. Trends in the regressions indicated ADG response to implantation was strongest for the light-stocking rate, but response to implantation decreased with increases in stocking rate. Stocking rate did not influence (P = 0.16) post-graze rectal temperature, but the regression intercept for implanted steers was 0.4^oC higher (P < 0.05) than for non-implanted steers, and the difference was consistent during the post-grazing monitoring phase. Rectal temperatures decreased (P < 0.001) to temperatures consistent with a healthy, unstressed animal between 6 and 8 d. There was a non-linear increase (P < 0.0001) in serum prolactin that did not stabilize by d 8. Results indicated that implantation with anabolic steroids increases ADG with lighter stocking rates but this benefit of implantation diminishes with increases in grazing intensity. Furthermore, heat stress of steers exhibiting symptoms of toxicosis can be alleviated in 6 to 8 days.