For The Crumble Topping For The Berry Filling

1. Preheat oven to 175 degrees C.
2. Combine the oats, flour, sugar, brown sugar, cinnamon and salt for the topping. Stir to combine. 
3. Pour in the melted butter and stir to incorporate then set aside.
4. In another bowl add the frozen berries, flour, sugar, salt, lemon juice and vanilla extract and toss gently to combine. 
5. Pour mixture into a square dish (8x8). Spread the topping ingredients evenly over the top .
6. Bake for 40-45 minutes until the topping is golden brown and berries are bubbling around the edges. 
7. Remove from the oven and cool for at least 7-10 minutes before serving. Serve with a scoop of vanilla ice cream, if desired.