Preheat your oven to 350°F (175°C).
In a large bowl, combine the sliced peaches and lemon juice. Toss to coat and then spread the mixture evenly in a greased 9x13-inch baking dish.
In another bowl, mix together the rolled oats, flour, brown sugar, granulated sugar, cinnamon, and salt.
Pour the melted butter over the oat mixture and stir until combined. If using, fold in the chopped nuts.
Sprinkle the oat mixture evenly over the peaches in the baking dish.
Bake in the preheated oven for 30-35 minutes, or until the topping is golden brown and the peaches are bubbly.
Remove from the oven and let cool for about 10 minutes before serving.