Mix the chopped rhubarb with the strawberry jam in an oven-proof serving dish. Place in the oven to cook for 10-15 mins until the rhubarb starts to soften. Sift over the cornflour and stir well to combine. Add the chopped strawberries.
To make the filling, stir the oats, flour and sugar together till combined. Pour in the melted butter and stir together with a fork till just mixed.
Pour the crumble topping over the rhubarb and return to the oven for 15-20 mins till golden and the fruit syrup is bubbling up at the edges.
