From America's Test Kitchen Season 1: Cookie Jar Classics
Big, moist, and craggy, oatmeal cookies are so good and so comforting, but also so hard to get just right. Too often, they have textural issues and are dry and brittle; other times, it’s the flavor that’s off, with cookies that lack any sign of oatiness. We wanted an oversized cookie with buttery oat flavor and the utmost chewiness.
After numerous rounds of testing, we discovered three key changes that made a significant difference in the research recipes we uncovered. First, we substituted baking powder for baking soda. The baking powder gave the dough more lift, which in turn made the cookies less dense and a bit chewier. Second, we eliminated the cinnamon recommended in lots of recipes; by taking away the cinnamon, we revealed more oat flavor. We wanted some spice, however, and chose nutmeg, which has a cleaner, subtler flavor that we like with oats. Finally, we increased the sugar in our cookies, and this made a huge difference in terms of texture and moistness.
Makes 16 to 20 large cookies
If you prefer a less sweet cookie, you can reduce the white sugar by one-quarter cup, but you will lose some crispness. Do not overbake these cookies. The edges should be brown but the rest of the cookie should still be very light in color. Parchment makes for easy cookie removal and cleanup, but it’s not a necessity. If you don’t use parchment, let the cookies cool directly on the baking sheet for two minutes before transferring them to a cooling rack.