At a whopping 1,628 calories per cup, butter is far from a low-fat food. However, it's hands down the best fat for baking because it provides superior taste, texture and moisture, without the trans fats of shortening. You can substitute applesauce for some of the butter in an oatmeal cookie, but don't remove the butter completely.
The Mixing Method
To substitute applesauce for butter in oatmeal cookies, cream the sugar and eggs together and then mix in the applesauce. Use a plain, no sugar applesauce for oatmeal chocolate chip cookies, or try cinnamon-flavored applesauce if you're making oatmeal raisin cookies.
It's All About Ratios
For best results, don't replace all the butter with applesauce. Instead, substitute applesauce for one-third of the butter. If you like crispy oatmeal cookies, add 1 tablespoon corn syrup to the dough. If you're satisfied with the results, you can try reducing the butter a bit more, but don't reduce it by more than half, or you'll end up with dry, crumbly cookies.
Expect Different Results
Cookies are more difficult than cakes and muffins to lighten. The butter in an oatmeal cookie provides moisture and flavor. It also adds texture and causes the cookie to spread out when baked. By substituting applesauce for the butter, you'll get a soft, puffy, cake-like cookie. Although you won't get a chewy, flat cookie, applesauce will keep the cookies moist, especially if you stick to the one-third ratio.
A Few Alternatives
Oatmeal cookies made with applesauce are tasty, but they're not quite the same as those made with butter. If you're unhappy with the results, try cutting the amount of applesauce even more or use low-fat yogurt or tahini paste instead. Add whole wheat flour and wheat germ to the cookies to boost their nutrition and make the cookies smaller so you're consuming fewer calories.