Preheat your oven to 350°F (175°C).
Line the muffin tin with paper liners or spray with non-stick cooking spray.
Cook the bacon in a skillet over medium heat until crispy, then crumble it.
In a large bowl, mix together the dry ingredients: flour, oats, brown sugar, baking powder, salt, and cinnamon.
In another bowl, whisk together the wet ingredients: milk, egg, melted butter, maple syrup, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Fold in the crumbled bacon.
Fill each muffin cup about 2/3 full with the batter.
Bake for 18-20 minutes, or until a toothpick inserted comes out clean. Let cool for 5 minutes before transferring to a wire rack.