Try this Oatmeal Breakfast Bars recipe.
A list of dry oats and whole wheat flour cannot reveal how these components behave under heat, where starch gelatinization dictates the final density. Whole wheat flour absorbs moisture differently than refined white flour due to the presence of bran and germ, requiring a thorough mix with the wet ingredients to prevent pockets of dryness. Old-fashioned rolled oats provide structural integrity by holding their shape during mixing, unlike instant oats which dissolve into mush. Whisk the dry ingredients thoroughly to distribute the two teaspoons of cinnamon and one teaspoon of baking powder evenly throughout the whole wheat flour. When folding in the diced banana, keep pieces uniform so moisture disperses predictably across the eight-by-eight-inch pan. Bake at 375 degrees Fahrenheit for 35 minutes, positioning your oven rack squarely in the center to encourage even browning. Assess doneness visually and tactually by inserting a wooden toothpick into the geometric center; it must emerge free of wet batter. Allow the baked slab to cool completely on a wire rack before slicing with a sharp chef knife into eight uniform portions.