Grease twelve 2-1/2-inch muffin cups or line with paper bake cups; set aside. In a medium bowl, combine oats and milk; let stand for 5 minutes. In a large bowl, combine flour, baking powder, salt, and cinnamon. Make a well in center of flour mixture; set aside.
Stir maple syrup, melted butter and egg into oats mixture. Add egg mixture all at once to flour mixture. Stir just until moistened (batter should be lumpy). Fold half of the pecans into the batter.
Spoon batter into prepared muffin cups, filling each two-thirds full. Sprinkle with remaining nuts. Bake in a 400 degree F oven for 15 to 18 minutes or until tops are golden and a wooden toothpick inserted in centers comes out clean. Cool in muffin cups on a wire rack for 10 minutes. Remove from muffin cups; serve warm. Makes 12 muffins.