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Grandma's Rhubarb Crisp

Grandma's rhubarb crisp is a traditional American dessert with tender rhubarb simmering into sweet syrup under a thick, buttery oat topping. Bake until golden brown and bubbling, then cool briefly for scoopable, spoon-tender filling.
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Prep Time 15 minutes
Cook Time 45 minutes
Cooling 10 minutes
Total Time 1 hour 10 minutes
Servings: 8 servings
Course: Dessert
Cuisine: American
Calories: 410
Ingredients Equipment Method Notes

Ingredients
  

For filling
  • 5 cup fresh rhubarb
  • 1.5 cup sugar
  • 3 tbsp all-purpose flour
For topping
  • 1 cup all-purpose flour
  • 1 cup brown sugar
  • 1 cup old-fashioned oats
  • 0.5 cup butter softened
  • 1 tsp cinnamon
To serve
  • 1 vanilla ice cream

Equipment

  • 1 sheet pan

Method
 

Preheat and prep the pan
  1. Preheat the oven to 350°F and grease a 9x13-inch baking dish, so it’s ready for even baking.
Make the rhubarb filling
  1. Combine fresh rhubarb, sugar, and all-purpose flour, toss well, and spread the mixture evenly in the prepared baking dish for a bubbling filling.
Assemble the oat topping
  1. Mix all-purpose flour, brown sugar, old-fashioned oats, softened butter, and cinnamon with a fork until crumbly, using the fork to create uneven oat clusters.
Bake
  1. Spread the crumb topping evenly over the rhubarb mixture so the top browns and turns crisp as it bakes.
  2. Bake for 40-45 minutes at 350°F until the topping is golden brown and the filling is bubbling, watching for deep toasted edges.
Cool and serve
  1. Let the crisp cool for 10 minutes to thicken slightly for clean scoops and a warm, syrupy bite.
  2. Serve warm with vanilla ice cream for a classic hot-and-cold contrast.

Notes

For the best texture, use rhubarb cut into 1/2-inch pieces so it bakes evenly and stays tender without turning stringy. Store covered in the refrigerator for up to 4 days and reheat in a 350°F oven until warmed through. Freezing is possible, but the oat topping may soften on thawing. For a lighter swap, use half the sugar with a like-for-like baking sugar alternative if your brand measures 1:1.