Key ingredients added to chewy oatmeal cookie recipes are melted butter, or shortening, and sweeteners, such as brown sugar, honey or molasses. Brown sugar helps cookies maintain a chewy texture by absorbing moisture after baking. The amount of fat added to the batter also determines the amount of moistness.
Most chewy oatmeal cookie recipes combine both white and brown sugars, which creates a balanced sweetness. As long as 1 or 2 cups of brown sugar is used, the cookies should turn out moist. In addition to brown sugar, some recipes include another sweetener, such as molasses, for extra moistness and flavor. Caution should be taken when adding liquids, including eggs, because too much liquid spreads out the batter, resulting in flat cookies. It may be necessary to add more flour to the mixture to balance out the additional liquid.
Another chewy cookie technique is to melt the butter before mixing it into the batter, which helps it blend in better with sugars. Cookies can be taken out of the oven a few minutes early to preserve moistness, as long as the edges are brown. Using less butter or shortening has the effect of creating cake-like cookies that puff up while baking. Opting for cake flour, instead of regular flour, and substituting baking powder for baking soda, creates lighter cookies as well.