Preheat the oven to 375 degrees F and grease 10 cups of a standard size muffin tin.
Place the oats into a food processor or blender. Grind for about 30 seconds or until they resemble a coarse flour.
Add the rest of the ingredients except the chocolate chips, if using.
Blend until very smooth, stopping to scrape down the sides of the bowl if needed.
Divide among 10 muffin cups. You want each cup to be about 3/4 full. Top with chocolate chips if using.
Bake for 20-22 minutes or until firm to the touch and lightly golden brown around the edges. Let cool in the pan for 5-10 minutes, then transfer to a wire rack (or just tilt a bit in the pan to let air flow underneath) to cool.
Serve warm, at room temperature, or chilled.
These muffins can store in the fridge in an airtight container for 3-5 days. Or in the freezer in a zip top freezer bag for up to 3 months. Thaw in the fridge or at room temperature.
Mini muffins: Use a mini muffin pan bake for 12-14 minutes or until a cake tester inserted into the centers comes out cleanly.
Dairy-free: Use nondairy milk.
To make without a blender: Use store-bought oat flour instead of rolled oats, mash the banana very smooth, and mix together in a mixing bowl.
You can use either Greek yogurt or milk in these muffins. Yogurt will make for slightly flatter muffins, but they will taste the same.
Add a few chocolate chips to the tops of each muffin if desired.
Serve cold or slightly warmed. Dice up for younger eaters as needed.