In a large bowl, toss together peaches, cranberries, apples, and 1 cup walnuts. Set aside.
In a medium bowl, stir together oats, granulated sugar, 1/2 cup brown sugar, the flour, 1 teaspoon cinnamon, and the 1/4 teaspoon salt. Add melted butter and lemon juice. Toss until combined. Add to fruit mixture. Toss to combine.
Press into a greased 9x9x2-inch baking pan. Bake in 350 degree F oven for 35 minutes or until apples are nearly tender.
Meanwhile, in another bowl, for topping, combine 1/2 cup brown sugar, 1 teaspoon cinnamon, and the dash salt. Cut in 1/4 cup butter until crumbly. Stir in 1 cup walnuts.
Spoon topping over hot mixture in pan. Return to oven. Bake 15 minutes longer or until topping is bubbly and apples are tender. Makes 6 servings.