Bring a large pot of water to a rolling boil. Score the skin of each peach with a small X, then carefully lower them into the boiling water for 30 to 60 seconds. Transfer the peaches to an ice bath to cool for a minute. Peel and slice the peaches into wedges.

While the peaches cool, hull the strawberries and either halve or quarter them depending on their size. Place the strawberries in a medium bowl.

In a large mixing bowl, gently toss the sliced peaches with the prepared strawberries.

Sprinkle granulated sugar, flour, ground cinnamon, and nutmeg over the fruit mixture. Use a gentle folding motion to mix.

Drizzle fresh lemon juice over the fruit mixture, gently stirring to incorporate.

Toss the coated fruit mixture until combined.

In another mixing bowl, whisk together the flour, rolled oats, brown sugar, baking powder, and salt.

Add cold unsalted butter and mix until crumbly.

If using, fold in the chopped nuts.

Preheat your oven to 375°F (190°C).

Lightly grease a 9x13 inch baking dish. Pour the fruit mixture into the dish and spread it out evenly. Sprinkle the topping mixture over the fruit.

Bake for 35 to 45 minutes, until the topping is golden brown.

Allow to cool for about 10 minutes before serving.

Serve warm with vanilla ice cream or whipped cream.