Preheat oven to 350F with the oven rack in the middle position.
Make the topping by mixing the topping ingredients together in a medium bowl until it resembles wet sand. Set aside.
Generously spray a 9 by 13 inch baking dish with nonstick spray.
In a large bowl, mix together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt. Stir to combine.
In a medium bowl, whisk together the eggnog, brown sugar, granulated sugar, eggs, and melted butter until combined.
Fold the eggnog mixture into the flour mixture and stir until the batter is combined.
Spread the batter into the prepared baking dish. Sprinkle the streusel mixture across the top of the batter.
Bake until the top is golden brown and cooked through (a toothpick inserted in the center should come out with just a few crumbs), approximately 40-45 minutes. Let rest 15 minutes before cutting and serving.