Preheat oven to 350.
In a large bowl stir together the flour, sugar, baking powder, baking soda, and salt.
Make a well in the dry ingredients, add the egg, melted butter, sour cream and beer. Stir until combined. Stir in the blackberries.
Spoon into muffin tins until each well is about 2/3 full. Sprinkle each muffin with brown sugar and oats.
Bake at 350 for 20 to 25 minutes (baking time will be less if you use unfrozen blackberries).