Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking pan or line it with parchment paper.
In a large mixing bowl, combine rolled oats, almond milk, melted coconut oil, maple syrup, brown sugar, and vanilla extract. Mix well until everything is fully combined.
Add baking powder, ground cinnamon, and salt to the oat mixture. Stir until just combined.
If desired, fold in chopped nuts and dried fruits for added texture and flavor.
Pour the mixture into the prepared baking pan, spreading it evenly.
Bake in the preheated oven for 25-30 minutes, or until the edges are golden brown and a toothpick inserted in the center comes out clean.
Allow the oatmeal bars to cool in the pan for about 10 minutes, then lift them out using the parchment paper (if used) and let them cool completely on a wire rack.
Once cool, prepare the glaze by mixing powdered sugar with milk until smooth. Drizzle the glaze over the oatmeal bars before slicing into squares.
Notes
Feel free to customize with your favorite nuts and dried fruits.