Preheat your oven to 350°F (175°C).
Grease your 9x13-inch baking dish with melted butter or non-stick spray.
Lay the thawed buttermilk pancakes in a single layer at the bottom of the prepared baking dish.
In a large mixing bowl, whisk together the eggs, heavy cream, whole milk, light brown sugar, vanilla extract, flour, quick-cook oats, and salt until smooth.
Gently fold in half of the frozen blueberries into the custard mixture.
Pour the custard mixture over the arranged pancakes.
Sprinkle the remaining blueberries on top and drizzle with melted butter, adding light brown sugar for a sweet crust.
Bake for 35-40 minutes, or until the top is golden and a toothpick inserted in the center comes out clean.
Let it cool for about 10-15 minutes before serving.