01 -
Preheat the oven to 400°F. Lightly butter a 2-quart casserole dish.
02 -
In a large bowl, combine all rhubarb filling ingredients. Evenly spread the mixture in the prepared casserole dish.
03 -
In a large bowl, mix oats, flour, sugar, cinnamon, and salt. Cut in the cold butter until the mixture forms crumbs.
04 -
Scatter the crumble topping evenly over the rhubarb filling. Bake in the oven for about 35 minutes, or until the topping is golden and the filling is bubbly. Let rest on the counter for 10 minutes before serving.