Combine all your ingredients for the cake except the blueberries.
Stir until completely mixed.
Then fold in your blueberries.
Pour into a greased 9 x 9 pan.
Prepare the topping. Mix your sugars, oatmeal, and cinnamon together. Then with a fork, smash in your butter until everything has a little butter mixed with it. Sprinkle topping over the top of cake mixture. Bake at 375 degrees for 45-50 minutes.