Preheat your oven to 375°F (190°C). In a large mixing bowl, gently toss the peach slices with sugar, cinnamon, and lemon juice until evenly coated. Transfer the fruit mixture to a buttered baking dish, spreading it into an even layer.
In another bowl, combine oats, flour, brown sugar, and ground ginger. Mix well to distribute the dry ingredients evenly.
Add the cold, small pieces of butter to the dry mixture. Use your fingers or a pastry cutter to work the butter into the oats until the mixture resembles coarse crumbs with some pea-sized pieces.
Sprinkle the oat topping evenly over the peaches in the baking dish, covering all the fruit surface.
Place the dish in the preheated oven and bake until the topping is golden brown and bubbling around the edges, about 40 minutes.
Remove the peach crisp from the oven and let it cool slightly; the topping will crisp up further as it cools. Serve warm, ideally with a dollop of whipped cream or a scoop of vanilla ice cream.
