Preheat and prep: Preheat your air fryer to 320°F (160°C) for 3–5 minutes. Lightly grease silicone muffin cups or use sturdy paper liners. Most basket air fryers fit 6 muffins at a time.

Hydrate the oats: In a bowl, mix oats and milk. Let sit for 5–10 minutes so the oats soften. This step keeps the muffins moist.

Mix dry ingredients: In a separate bowl, whisk flour, baking powder, cinnamon, salt, and sugar until no lumps remain.

Combine wet ingredients: To the oat-milk mixture, add egg, yogurt, oil, and vanilla. Whisk until smooth.

Bring it together: Add the dry ingredients to the wet. Stir gently just until combined. The batter should be thick but scoopable. If using juicy fruit like blueberries, fold them in now.

Fill the cups: Divide the batter among the muffin cups, filling each about 3/4 full. Sprinkle tops with a few oats or coarse sugar if you like.

Air fry: Place the filled cups in the air fryer basket. Cook at 320°F (160°C) for 10–12 minutes, or until the tops are set and a toothpick comes out mostly clean with a few moist crumbs.

Cool slightly: Let muffins rest in the cups for 5 minutes, then transfer to a rack. This helps them set and prevents sticking.

Repeat: If you have more batter, repeat with the remaining cups. Cooking time may vary by air fryer model, so keep an eye on the first batch.