Trimming Back the Fat

• Most cookie recipes work best if you reduce the amount of oil when substituting it for shortening. California State University at Sacramento recommends using 3/4 cup of oil for each cup of solid fat required in your recipe. If the recipe requires you to melt the shortening before combining it with other ingredients, however, you should substitute an equivalent amount of oil.

Texture Transmutations

• Shortening and other solid fats coat the individual particles of sugar and flour in cookies, making them lighter and flakier. If you substitute oil for these fats, your cookies could be heavy or cake-like in texture. Some cookies also become greasy when you make them with oil. You may also experience changes in flavor. Stronger-tasting cooking oils such as olive or peanut can change the final product significantly.

Stopping the Spread

• Oil reacts differently to heat than shortening. It tends to saturate the cookie and can make it come out flatter. Oil-based cookies also tend to spread more quickly than those made with shortening. This might produce a more irregular shape. Chilling the dough before you bake or reducing the amount of oil you use can mitigate these problems somewhat.

Keeping It Solid

• Cookies work best when you substitute solid fats for shortening instead of oil. Coconut oil works as a direct substitute for butter or shortening. Palm oil, margarine and butter also work better than oil, but they may cause your cookies to be crispier or more likely to spread. Substitute them for shortening at a one-to-one ratio.