Preheat the oven to 350F. Line pan with parchment paper.
Combine all the ingredients in a blender or food processor and blend until the batter is mostly smooth. You likely will have some oats that are not entirely ground up, but the rest of the batter should be smooth.
Pour the batter into the prepared pan and bake for 15-20 minutes, until the tops are medium golden brown. Careful not to undercook the brownies as the center will remain gooey.
Allow the brownies to cool completely before cutting.