Oyster mushrooms (Pleurotus spp.) can turn grape pomace into edible biomass, creating a clean “waste-to-food” loop for wineries and growers. Per liter of wine, about 0.16–0.17 kg of grape pomace is generated (roughly 1 kg per 6 liters), and using it as a substrate can support mycelial growth and fruiting while boosting “functional” components in the harvested mushrooms with reported increases include ergosterol, β-glucans, resveratrol, and antioxidant activity.