Ingredients

• 1 cup all-purpose flour
• 1 cup brown sugar
• 3/4 cup oats
• 1/2 cup melted butter
• 1 teaspoon ground cinnamon

• 4 cups diced rhubarb
• 1 cup white sugar
• 1 cup water
• 2 tablespoons cornstarch
• 1 teaspoon vanilla extract

Directions

1. Preheat oven to 350 degrees F (175 degrees C). Grease a 9×13-inch baking dish.
2. Mix flour, brown sugar, oats, butter, and cinnamon together in a bowl until crumbly. Press 1/2 of the oat mixture into the bottom of prepared baking dish. Sprinkle rhubarb over oat mixture.
3. Combine white sugar, water, cornstarch, and vanilla extract in a saucepan over medium heat; cook and stir until thick and clear, about 5 minutes. Pour sugar mixture over rhubarb. Sprinkle remaining oat mixture over rhubarb.
4. Bake in the preheated oven until crisp is lightly brown and bubbling, about 1 hour.