Preheat the oven to 180ºC (350ºC). Line a 9” x 9“ square baking pan with parchment paper, and set aside.
Before beginning, ensure the butter is cubed and softened to room temperature.
In a large mixing bowl add flour, oats, and sugar. Mix until well combined.
Add softened butter and using your hands, rub the butter into the flour until it forms a crumbly dough.
Transfer about ⅔ of the crumble dough into the lined pan and firmly press it in to form the base.
Pour the jam over the base, spread it out and leave a small gap between the jam and the edge of the base all the way around.
Sprinkle over the remaining crumble.
Bake for 35-40 minutes or until the crumble topping has turned lightly golden and the jam is bubbling.
Remove and allow the crumble to cool completely in the pan.
Carefully transfer to a wire rack to cool further.
Slice into bars and enjoy!