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Easy Oatmeal Rhubarb Bars: Rustic Summer Dessert


  • Author: Emma
  • Total Time: 1 hour
  • Yield: 12 bars (3×4 grid) 1x
  • Diet: Vegetarian

Description

A buttery oat crust and crisp oat crumble sandwich a tart-sweet, lemon-kissed rhubarb filling—perfect for summer gatherings, afternoon tea, or make-ahead snacks.


Ingredients

Scale

2 cups rolled oats

1 cup all-purpose flour

1 cup brown sugar

1 cup chopped rhubarb

1/2 cup unsalted butter

1/2 teaspoon baking powder

1/2 teaspoon cinnamon 

1/4 teaspoon salt

1/2 cup water


Instructions

 

  1. Preheat & Prep
    Preheat oven to 180 °C (350 °F). Line a 9×13 inch pan with parchment, leaving a 1″ overhang for easy removal.

  2. Make Crust
    In a bowl, whisk oats, flour, sugar, salt, and cinnamon. Add butter; cut in with a pastry cutter until coarse crumbs form.
    • Reserve 1¼ cups for the topping.
    • Press the remaining mixture firmly into the pan. Chill 10 minutes.

  3. Assemble Filling
    Toss rhubarb with sugar, cornstarch, vanilla, and lemon zest. Spread evenly over chilled crust.

  4. Add Topping
    Sprinkle reserved oat mixture over the rhubarb layer.

  5. Bake & Cool
    Bake 35–40 minutes until topping is golden and filling bubbles. Cool completely on a wire rack (about 1 hour) before slicing into 12 bars.

 

Notes

Bolder Rhubarb Flavor: Use 3–4 cups rhubarb; reduce water to ¼ cup (or omit) to avoid sogginess.

Nutty Upgrade: Fold ½ cup chopped walnuts or pecans into the topping.

Citrus Twist: Swap lemon zest for orange or lime.

Make-Ahead: Assemble, cover, and refrigerate unbaked up to 24 hours; bake straight from the fridge, adding 2–3 minutes.

Storage: Airtight container at room temperature up to 2 days or refrigerated up to 5 days. Freeze layered between parchment up to 1 month.

  • Prep Time: 20 minutes
  • Cook Time: 35–40 minutes
  • Category: Dessert / Snack
  • Method: Baking
  • Cuisine: American farmhouse

Nutrition

  • Serving Size: 1 bar
  • Calories: 230 kcal
  • Sugar: 12 g
  • Sodium: 120 mg
  • Fat: 9 g
  • Saturated Fat: 5 g
  • Unsaturated Fat: 3 g
  • Trans Fat: 0 g
  • Carbohydrates: 32 g
  • Fiber: 3 g
  • Protein: 3 g
  • Cholesterol: 30 mg

Keywords: Oatmeal Rhubarb Bars, Rustic Dessert, Summer Baking