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Grandma's Rhubarb Crisp

Grandma's rhubarb crisp is a traditional American comfort food with tender rhubarb bubbling under a thick, buttery oat topping. Bake until the oats turn golden brown and crispy, then cool briefly for a warm scoopable texture.
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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: 320
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

Equipment

  • 1 sheet pan

Method
 

Prep and fill
  1. Preheat the oven to 350°F and grease a 9x13-inch baking dish. This prevents sticking so you can scoop tidy portions.
  2. Combine rhubarb, sugar, and flour, tossing until the rhubarb is evenly coated. Spread the mixture in the prepared dish for an even bubbling layer.
Make topping and bake
  1. Mix flour, brown sugar, oats, softened butter, and cinnamon with a fork until crumbly. Leave pea-size crumbs so the topping browns into a crisp top.
  2. Spread the crumb topping evenly over the rhubarb mixture. Cover all the filling so it crisps uniformly as it bakes.
  3. Bake for 40-45 minutes at 350°F until the topping is golden brown and the filling is bubbling. Look for a crisp, set top with active syrup bubbling around the edges.
Cool and serve
  1. Let the crisp cool for 10 minutes before serving warm. The syrup thickens slightly for a scoopable, spoon-friendly texture.

Notes

Pro tip: use fresh rhubarb that’s bright and firm, and cut it into 1/2-inch pieces for consistent tenderness. Store covered in the refrigerator up to 4 days; reheat portions in the oven at 300°F until warmed and lightly crisped. Freezing is not recommended because the topping can soften after thawing. For a dairy-light option, replace the butter with a 1:1 plant-butter stick and keep the topping crumbly before baking.