Preheat oven to 350 degrees F. Grease an 8 by 8-inch baking dish
In a medium bowl combine the oats, brown sugar, sugar, salt, and baking powder, and mix until combined.
In another bowl combine the peanut butter, milk, and vanilla, and mix until well blended.
Pour the wet ingredients into the bowl with the dry ingredients, and mix until well blended.
Pour into the prepared baking pan. Bake in a preheated oven for 35 to 40 minutes or until the center is set and the edges pull slightly away from the edge of the pan.
Serve warm.