Prep the Oven and Tin
Preheat your oven to 385°F.
Line a 12-cup muffin tin with paper liners, silicone cups, or grease the cups thoroughly with cooking spray.
Add the liquid and soft ingredients to your blender or food processor first. Use bananas, Greek yogurt, maple syrup, eggs, baking powder, baking soda, vanilla extract, cinnamon, and salt.
Blend the Batter
Add the 2 cups of rolled oats last on top of the wet ingredients to keep the oats from getting stuck under the blades.
Blend or process on high for about 45 to 60 seconds until the oats are completely broken down and the batter is creamy and smooth.
Remove the blender pitcher or food processor bowl from the base.
Remove the blade carefully if using a food processor.
Divide the batter and add the berries and nuts ** see notes
Divide the smooth batter evenly among the 12 prepared muffin cups.
Top each muffin generously with the blueberries and nuts pressing them down just slightly into the batter. Gently stir the berries and nuts in the batter with a skewer or chop stick.
Bake at 385°F for 15 to 18 minutes. Check them with a toothpick in the center around the 15-minute mark. They are done when the toothpick comes out clean or with a few dry crumbs.
Cool
Remove from the oven and let the muffins cool in the hot tin for 10 minutes.
Transfer them to a wire rack to finish cooling completely.