Pre-heat oven to 350 degrees and lightly oil or butter a rimmed sheet pan or 12 x 16 (or similarly sized) baking dish.
Put the oats, flour, nuts, cinnamon, salt, and baking powder in a bowl. Mix well. Add melted butter, oil, honey or maple syrup, and molasses. Mix until the topping is crumbly and looks like little pebbles. Pat down half this crust mixture in the bottom of the baking pan. A rolling pin or the back of a wide spoon is helpful to make it even all the way to the edges. Leave the rest of the crust mixture in the bowl while you make the filling.
Put the chopped apples, applesauce, cranberries or raisins, honey or maple syrup in a bowl and mix well. Pour the apple mixture on top of the crust in the baking pan. Using the back of a spatula, press the mixture down until the top is flat and even.
Top the apple mixture with the crust mixture left in the bowl and pat it down. Put the pan in the oven and bake until the top of the apple mixture is lightly browned and the apples are soft, 40 – 45 minutes.
When the pan comes out of the oven, pat down the mixture again with spatula. Allow to cool before cutting in to squares.