Chop the rhubarb into 1-inch pieces and place in a mixing bowl.
4 cups Rhubarb, chopped
Sprinkle granulated sugar over the rhubarb, mixing well to combine.
4 cups Rhubarb, chopped, 1 cup Granulated sugar
In a separate bowl, combine flour, oats, brown sugar, melted butter, and cinnamon until crumbly.
1 cup All-purpose flour, 1 cup Rolled oats, 1/2 cup Brown sugar, 1/2 cup Butter, melted, 1 teaspoon Ground cinnamon
Pour rhubarb mixture into a baking dish and evenly spread the crumb topping over it.
4 cups Rhubarb, chopped, 1 cup Granulated sugar, 1 cup All-purpose flour, 1 cup Rolled oats, 1/2 cup Brown sugar, 1/2 cup Butter, melted, 1 teaspoon Ground cinnamon
Bake in the preheated oven for 35-40 minutes, until the topping is golden brown and the rhubarb is bubbling.
Remove from the oven and let cool slightly before serving.
Notes
Serve warm, optionally topped with vanilla ice cream or strawberry compote.