To avoid the disappointment of a sunken quick bread, make sure you measure out all the ingredients correctly, especially the baking powder. Be careful not to overmix the batter, because this can lead to a dense and unevenly baked loaf. Also make sure you do not underbake your bread. Insert a toothpick into the center of the bread and only if it comes out clean (or with a few moist crumbs stuck to it) you can remove the loaf from the oven.