Preheat your oven to 350°F (175°C).
In a large bowl, combine sliced peaches, sugar, and lemon juice.
Transfer the peach mixture into a greased 9x9-inch baking dish.
In another bowl, mix oats, flour, brown sugar, and cinnamon.
Pour melted butter into the oat mixture and stir until combined.
Spread the oat mixture evenly over the peaches in the baking dish.
Bake in the preheated oven for 30 minutes, or until the topping is golden brown.
Remove from the oven and let it cool slightly.
Serve warm with ice cream or whipped cream, if desired.
Enjoy your homemade peach crisp!