what is oleo in a recipe

Oleo is another word for margarine or oleomargarine. It is a plant-based spread made from refined oils and water, developed to taste like butter. Oleo is used as a substitute for butter in many recipes, especially in older recipes. If a recipe calls for oleo, it can be replaced with butter or margarine, but be aware that margarine has a much higher water content than butter, so the results may not be exactly the same.