Preheat the oven to 400°F, and lightly grease an 8-inch round, 8 x 8-inch baking dish, or 2-quart dish.
For the Crumb Topping
In a medium bowl, use a pastry cutter or your hands to combine the topping ingredients until well mixed.
1 cup old-fashioned rolled oats, 6 tablespoons unsalted butter, ½ cup all-purpose flour, ½ cup brown sugar, ¼ cup granulated sugar, ½ teaspoon ground cinnamon, ½ teaspoon salt
Transfer the crumb topping to the refrigerator while you prepare the filling.
For the Rhubarb Filling
Add the rhubarb, brown sugar, ¼ cup of water, vanilla and cinnamon to a medium saucepan. Bring to a simmer over medium heat, and cook for about 5 minutes.
6 cups rhubarb, ¾ cup light brown sugar, 2 teaspoons pure vanilla extract, 1 teaspoon ground cinnamon
While the rhubarb mixture cooks, make a slurry by mixing the remaining ¼ cup cold water and 2 tablespoons of cornstarch until smooth. Add the slurry, and stir until the mixture beings to thicken, about 2 to 3 minutes.
2 tablespoons cornstarch
Add the rhubarb mixture to the prepared baking dish then sprinkle the crumb topping over the top.
Bake for 30 to 35 minutes or until the top turns a light golden color and the center jiggles slightly. The filling will be bubbly around the edges.
Allow the crisp to rest for 5-10 minutes before serving. Serve warm with vanilla ice cream!
Notes
*The calories listed are an approximation based on the ingredients in the recipe card and a serving size of 1 cup of rhubarb crisp. Actual calories will vary.*Skip to Storage Info.