This study aimed to investigate the impact of the oxidative potential of turkeys fed a diet with alfalfa protein concentrate (APC), used throughout the rearing period or periodically at 2-wk intervals. The research material consisted of 6-wk-old BIG 6 turkey hens kept in pens, 5 birds per pen in 6 replicates. The experimental factor was the addition of APC to the diet in the amount of 15 or 30 g/kg of diet. APC was administered in 2 ways: birds received a diet with APC throughout the experiment or periodically. In the latter case, the birds received the diet with APC for 2 wk, and then for 2 wk they received the standard diet without APC. Levels of nutrients in the diet; flavonoids, polyphenols, tannins, and saponins in APC; uric acid, creatinine, bilirubin, and some antioxidants in the blood; and enzyme parameters in the blood and tissues of turkeys were determined. The use of APC in the diet stimulated antioxidant processes, which could be seen in the values of the pro-oxidant–antioxidant parameters of the tissues and blood plasma of turkeys. The significant reduction in the H2O2 level (P = 0.042) and slight reduction in the MDA level (P = 0.083), accompanied by an increase in catalase (P = 0.046) activity in the turkeys continuously receiving APC in the amount of 30 g/kg of diet, as well as the increase in plasma antioxidant parameters (vitamin C, P = 0.042 and FRAP, P = 0.048) in these birds, reflects improvement in their antioxidant status. Thus continuous use of the APC supplement in the amount of 30 g/kg of diet proved to be a better feeding practice to optimize oxidative potential than periodic inclusion of APC.