Preheat oven to 375. To make cake, mix oil, cream cheese, egg and half and half in a bowl. Mix well.
In another bowl, sift together flour, sugar, baking powder and salt. Add to wet ingredients and mix well.
to make topping, mix brown sugar, flour, cinnamon, nutmeg, pecans and melted butter in bowl. Pour cake batter into a greased 9 x 9 inch pan. Spread blueberries evenly over batter Sprinkle evenly with topping. Bake for 20 to 25 minutes or til toothpick inserted in center comes out clean.