With a stand mixer, mash the bananas until smooth. Add the honey, canola oil, flaxseed, and vanilla. Mix together on medium speed until all ingredients are combined thoroughly.
In another bowl, whisk together the whole wheat flour, oats, baking soda, salt, and nutmeg.
Add dry ingredients to the wet ingredients and mix until ingredients are just incorporated. Batter will be lumpy. Fold in blueberries with a rubber spatula.
Divide muffin batter among muffin cups and fill each about ¾ full.
Bake for about 30-45 minutes until a toothpick comes out clean.