The increasing demand for sustainable and plant-based food products has encouraged the development of innovative beverages based on traditional cereals. This study presents the formulation of an oat-based milk using ancient oat varieties cultivated in the Lazio region, Tuscia area, Central Italy, aiming to promote local biodiversity and support a short food supply chain. The beverage was produced through enzymatic hydrolysis of dehulled oat grains, preceded by a careful selection of enzymatic blends and optimization of their working conditions (temperature and reaction time). Extra virgin olive oil was added as a natural emulsifier, and a small amount of salt was used to improve product stability. The final recipe was adapted in collaboration with local producers to ensure feasibility for small-scale production. Process performance was evaluated through key technological parameters, including extraction yield, emulsion stability, and viscosity. Compositional analyses confirmed the presence of complex carbohydrates, beta-glucans, and a balanced macronutrient profile, without the addition of sugars or synthetic additives. Sensory evaluation, carried out by a trained panel, highlighted a pleasant cereal aroma, smooth mouthfeel, and good overall acceptability. This study demonstrates the feasibility of producing a clean-label, nutritionally balanced, and locally sourced plant-based milk. The use of ancient oat varieties, combined with a tailored processing approach and involvement of local actors, represents a sustainable strategy to meet consumer demand for healthy and eco-friendly dairy alternatives.