Move the oven rack to the center of the oven. Preheat the oven to 350 degrees.
Prepare an 8x4 loaf pan by spraying the pan lightly with nonstick spray and then placing a piece of parchment paper into the pan.
Using a heavy-duty blender or food processor, pour in the milk, sugar, peanut butter, and eggs. Process for 1 to 2 minutes until a smooth batter (depending on the strength of your appliance).
Next place the flour, oats, baking powder, and salt and process until smooth (about 1 minute). If your appliance is lower wattage just add the dry ingredients gradually.
Pour batter into the prepared loaf pan.
Place in the oven and bake for 1 hour and 10 minutes or until a toothpick comes out clean or with just a few crumbs on it.
Set a timer for 50 minutes and check the bread to make sure the top is not getting too brown. If it is getting too brown, you can cover it loosely with foil. Then continue baking.
Remove from the oven and let rest in the pan for 10 minutes on a cooling rack before removing.
Allow the loaf to completely cool before slicing to serve!