Gather all ingredients. Preheat the oven to 425 degrees F (220 degrees C). Grease 12 standard muffin cups or line with paper muffin liners.
Combine milk and oats in a small bowl; let soak for 15 minutes.
Beat together egg and oil in a large bowl; stir in oat mixture. Sift together flour, sugar, baking powder, and salt in a separate bowl.
Stir flour mixture into wet ingredients until just combined.
Spoon batter into the prepared muffin cups until ⅔ full.
Bake in the preheated oven until a toothpick inserted into the center of a muffin comes out clean, 20 to 25 minutes.
