In a small bowl, combine oats and milk. Let stand for 5 minutes.
In a large bowl, whisk together flour, baking powder, salt, and cinnamon.
Add maple syrup, butter, and egg to the oat mixture.
Pour the oat mixture into the flour. Stir until just moistened.
Fold in half of the pecans. Spoon batter into a muffin tin lined with 12 paper liners. Sprinkle with reserved pecans. Bake in a preheated 400-degree oven for 15 to 18 minutes.