Preheat the oven to 350 degrees and spray a loaf pan with non stick spray, set aside.
In a large bowl using an electric hand mixer, blend together the eggs, vegetable oil, milk and yogurt. In a separate bowl, combine the dry mix with the oats, brown sugar and cinnamon. With the hand mixer on medium low speed, slowly add the dry ingredients to the wet and blend until a batter forms. Pour the batter into the prepared pan. Peel and slice the apple, lay apple slices flat on top of the batter in the pan, overlapping each slice slightly.
Using your hands, combine all of the ingredients for the topping together in a small bowl. Sprinkle the topping mixture evenly over the apple slices. Bake for 50-60 minutes or until a toothpick inserted into the center comes out clean. Cool 15 minutes in the pan, then remove and allow to cool on a rack before serving.