Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking dish.
In a large mixing bowl, combine the rolled oats, milk, diced apple, brown sugar, cinnamon, vanilla extract, and salt. Stir until well mixed.
In a separate bowl, beat the eggs and then add them to the oat mixture. Stir until fully incorporated.
If using, fold in the chopped nuts and dried fruit.
Pour the mixture into the prepared baking dish, spreading it evenly.
Bake in the preheated oven for 30-35 minutes, or until the top is golden brown and the oatmeal is set.
Allow to cool for 5-10 minutes before slicing and serving.