Preheat oven to 400 degrees and spray tin with non-stick cooking spray. My most favorite is called Baker's Joy (it has flour added in). You could also use a silicone muffin pan. (I don't recommend using paper liners for these.
Place all of the liquid ingredients in the blender (including pumpkin), and then blend adding oats in 1/2 c at a time until smooth. You may need to stop the blender a few times to stir. Stir in chopped walnuts after blending is complete.
Divide batter among 12 muffin cups and bake for 20 min. or until toothpick comes out clean.