Substituting vegetable oil for butter in cooking many items is a viable option and a healthy decision. Vegetable oil contains polyunsaturated and monounsaturated fats, while butter contains saturated fat.
To substitute oil for butter, use 4 tablespoons of vegetable oil or 3 tablespoons of olive oil for every 1/4 cup butter called for in breads and muffins. However, oil is a poor substitute for butter in baked goods such as cookies or cakes where the recipe calls for creaming the butter with sugar and eggs.
Vegetable oil may also be used in place of butter when stir frying and may be used as alternative to butter as a condiment on bread by serving a small amount of oil and some spice for dipping.