Preheat the oven to 425°F. Spray a 12-count muffin pan with nonstick spray or use muffin liners. This recipe makes about 15 muffins, so prepare a second muffin pan the same way.
Place the oats1 in a blender or food processor. Blend or process until powdery and flour-like. Then, add the rest of the ingredients, in the order listed, except for the 3/4 cup of add-ins. Blend or process until combined, scraping down the sides or bottom as needed. Stir in the add-ins.
Pour the batter into the prepared muffin pans, filling them all the way to the top. Top with a few oats, if desired.
Bake for 5 minutes at 425°F then, keeping the muffins in the oven, reduce the temperature to 350°F. Bake for an additional 6-8 minutes or until a toothpick inserted into the center comes out clean— these took 7 additional minutes. The total baking time for these muffins is 12-13 minutes, give or take. Allow the muffins to cool for 5 minutes in the muffin pan, then transfer to a wire rack to finish cooling.
Muffins stay fresh covered at room temperature for up to 2 days or in the refrigerator for up to 1 week.
Make ahead tip: These muffins freeze well. Store in air-tight bag or container and freeze up to 3 months. Allow to thaw on the counter or defrost in the microwave.Make these vegan: Use 2 chia seed eggs (1 chia seed egg = 1 Tablespoon chia seeds + 2.5 Tablespoon water + let sit for a few minutes) with dairy-free yogurt mentioned below.1To make these gluten-free, use certified gluten-free old fashioned oats. I prefer the Bob's Red Mill brand.2Any fat % of Greek yogurt can be used for these. To make this dairy-free, you can use dairy-free yogurt. I prefer Kite Hill plain unsweetened since it has a very plain flavor.3The total add-ins for these muffins are 3/4 cup— use whatever you prefer (chocolate chips, chopped walnuts, etc.)