<p>This study investigates the effects of red cabbage waste (RCW) as a dietary supplement on the performance, egg quality, and oxidative stability of yolk in laying Japanese quails. Given its rich phenolic content, RCW has been investigated as a natural feed additive to reduce food waste and enhance poultry diets. In a six-week trial, 120 quails were divided into 4 groups with 5 replicates and fed diets with 0.0%, 0.5%, 1.0%, and 2.0% RCW. Performance parameters, internal and external egg quality, and antioxidant status were measured. RCW supplementation had no significant impact on overall quail performance. Quails fed with 0.5% RCW showed notable improvements in internal egg quality, especially in the albumen index, Haugh unit, and eggshell thickness. Additionally, incorporating 0.5% RCW into the diet improved the yolk’s antioxidant activity, as evidenced by reduced MDA levels. However, other egg quality traits, including the antioxidant capacity of the yolk, had deteriorated with concentrations above 0.5%, indicating that a moderate inclusion of 0.5% RCW is the most favourable option. The findings underscore that RCW could be sustainably used to improve egg quality without compromising performance, while managing food waste, presenting a potential circular economy solution. Nevertheless, further research is encouraged to optimize RCW levels and fully understand its benefits in poultry feed.</p>