Expert Tip: Using quick-cooking oats ensures that the oats fully soften during the baking time specified in the recipe. They absorb moisture more quickly and help bind the ingredients together, creating a crumbly texture that's ideal for bars and cookies. If you were to use old-fashioned rolled oats, the bars might turn out chewier and have a coarser texture because those oats take longer to cook and don't break down as much during baking.