Avocados can be used as a substitute for butter or oil in your favorite baked good recipes like cookies, cakes or muffins. The result may vary slightly by recipe. Assume a one-to-one substitution of avocado for butter in your recipe. However when substituting avocado for oil it may be necessary to add another liquid to "thin out" thicker batters or mixes. Experiment a bit with the recipe.
I have found you will get better results if you only substitute half the amount of butter in your recipe for mashed avocado. If you substitute the whole amount, you'll end up with baked items that will not raise as high. One avocado yields about three-quarters of a cup.
Avocados contain a high water content, so they yield a softer, moister baked good. You may also note the color, the pretty green. This can be a plus depending on what you are making.