This study was conducted during the early summer months in a feedlot in Nebraska. The average temperature (including night readings) was approximately 23 C, and humidity averaged approximately 85%. Three dietary regimes were used: ad lib, or 75% ad lib for the first 21 or 42 days of the 63 day study. Tympanic temperatures (ear canal) were used as indicative of deep body temperature and thus heat stress. Limiting the amount of feed resulted in reduced tympanic temperatures, but as much as 0.5 C, indicating a reduction in heat stress. Although average panting and bunching scores (indicative of heat stress) were similar among treatments, the proportion of animals that were panting was higher for the ad lib fed animals. Dark coloured cattle had higher panting scores and higher tympanic temperatures (up to 0.2 C) than did light coloured cattle, indicating that solar radiation was a significant contributor to heat stress. These results suggest that restricting feed intake during periods of hot weather will reduce the severity of heat stress. Using light coloured cattle would also reduce the severity of heat stress, as would the provision of shade.