To prepare the topping: In a medium sized mixing bowl combine oats, flour, brown sugar, cinnamon, nutmeg and salt. Add in the butter and vanilla and use a fork to blend the ingredients together until crumbly in texture, about the size of peas. It's okay if there is a little bit of powdery flour or oats that don't incorporate.
Preheat the oven to 350°F. Spray a 9x9” baking dish with non-stick cooking spray and set aside.
In a large mixing bowl combine the strawberries, cornstarch, brown sugar, sugar, lemon juice, vanilla and salt. Toss well to coat, then set aside.
Transfer the strawberry filling into the prepared baking dish, then evenly sprinkle the crumble topping over top.
Bake in the preheated oven on the center rack for 30-40 minutes, until the strawberries are bubbling and the liquid is thicker and darker around the edges of the pan. (the cornstarch is helping to thicken as it bubbles).
The crumble topping should be golden brown. Once baked, remove from the oven and let cool for at least 10 minutes before serving.