Preheat oven to 350ºF. Lightly grease a 9″ square baking dish with nonstick spray.
Strawberry Apple Filling
In a large bowl, toss together the fruit, sugar, flour, and lemon/lime juice. Transfer to the prepared pan.
Crumble Topping
Place the butter in a skillet set over medium-low to medium heat. Cook until the butter melts, foams up, and turns golden-brown, whisking occasionally. Remove from heat and set aside.
Meanwhile, in a large bowl, whisk together the brown sugar, flour, pecans, oats, graham cracker crumbs, cinnamon, baking powder, baking soda, and salt. Add the browned butter and mix in with a spatula until all of the dry ingredients are well-coated and the mixture is crumbly. Sprinkle crumble topping evenly over fruit in prepared pan.
Bake in preheated oven for about 40 minutes, until top is golden-brown and filling is bubbling around edges.