Cattle grazing native rangelands during winter must balance forage intake, a source of energy gain, while minimizing thermal stress, a potential source of energy loss. Another source of energy loss is related to time spent on different activities by cattle. Natural or man-made shelter may alter time spent on different activities. The objective of this was to determine if access to windbreaks altered diurnal activity patterns of beef cattle grazing a windy, foothill range site during winter, and if diurnal activity patterns could be related to weather. Diurnal activity patterns of cattle could be observed with and without access to windbreaks for two winters on an exposed pasture in southwest Montana. Actual use of windbreaks was only recorded in winter 2. Time spent behind windbreaks ranged from 0 to 30%. Activity pattern of wind break and nonwindbreak cattle differed in subtle ways indicating they used similar behaviours to minimize energy expended and o maximize energy gain. Wind velocity had minimal effect on grazing time, presumably because high wind velocities were associated with relatively warm days, or the animals were in sufficient condition to tolerate high wind velocities. Instead of minimizing energy expended by lying down during extreme cold, cattle spent more time standing, which maximizes heat gain from solar radiation. At times, winter weather may be energetically demanding, but results of this study indicate that these cows, under long-term selection for performing under such winter conditions, adjust physiologically and behaviourally to daily and seasonal weather events, as long as they are in sufficient body condition.