Gather all ingredients and lightly grease a 9x13-inch baking dish.
Heat brown sugar, butter, and corn syrup in a small saucepan over medium heat. Cook and stir until mixture begins to boil; remove the mixture from heat, and pour into the prepared baking dish.
Place bread slices atop brown sugar mixture.
Whisk eggs and eggnog together in a large bowl; pour over bread slices. Cover the baking dish with aluminum foil, and refrigerate 8 hours to overnight.
Preheat the oven to 325 degrees F (165 degrees C). Remove the baking dish from the refrigerator.
Bake in the preheated oven, covered, until custard has set, about 35 to 40 minutes. Increase heat to 375 degrees F (190 degrees C); remove the aluminum foil, and continue baking until the the top is golden brown, about 5 minutes more.