Resident birds in temperate areas respond to seasonally fluctuating temperatures by adjusting their physiology so as to match thermogenic requirements of their environment. Climate change is predicted to increase the frequency of heat waves, increasing the likelihood that birds will face environmental mismatch. Changes in BMR due to seasonality or anomaly events should show effects to the oxidative stress system. We examined the effects of chronic and acute heat exposure on muscle and brain tissue total antioxidant capacity, enzymatic activities of catalase (CAT), and glutathione peroxidase (GPx) and lipid peroxidation (LPO) damage in two temperate bird species of differing body masses and ecological strategies, the black-capped chickadee (Poecile atricapillus) and the rock pigeon (Columba livia), across three seasons. We found that heat stress did not alter oxidative stress in either species or tissue. But, in muscle, rock pigeons and black-capped chickadees demonstrated similar seasonal changes where peroxyl scavenging capacity was highest in the fall, hydroxyl scavenging capacity was higher in fall and summer. CAT activity was lowest in the fall and highest in the summer, GPx activity was highest in the fall, and LPO damage was highest in the summer but lowest in the fall.  In brain, we found that scavenging capacity to hydroxyl radicals was highest in fall and summer for rock pigeons, whereas it was only elevated in the summer for black-capped chickadees. Our data suggest that the oxidative stress system is slow to change seasonally.