Easy Rhubarb Crumble Bars

Bake easy rhubarb crumble bars with a tart, less-sweet filling and buttery oatmeal crumble. A perfect small batch recipe for rhubarb lovers!

Course Dessert

Cuisine American

Keyword bars, crumble bars, gluten-free rhubarb bars, rhubarb, small batch rhubarb bars, tart rhubarb oatmeal bars, vegan rhubarb bars

Prep Time 15

Cook Time 30

Total Time 45

Servings bars

Calories 534kcal

Preheat Oven: Preheat to 375°F (190°C). Grease a 9x9-inch pan or line with parchment (overhang for easy removal).
Prepare Filling: Dissolve cornstarch in cold water. In a saucepan, combine rhubarb, sugar, vanilla, and slurry. Cook over medium heat, stirring, until thick like jam (5–8 min). Cool slightly. Drain excess liquid if watery.
2 tbsp. cornstarch, 3½ tbsp. cold water, 2 c. rhubarb, ¾ c. granulated sugar, 1 tsp. vanilla extract
Prepare Crumble: Whisk oats, flour, brown sugar, baking soda, and salt. Cut in cold butter with a pastry cutter or fingers until coarse crumbs with pea-sized pieces form.
1¼ c. quick oats, 1¼ c. unbleached all-purpose flour, ½ c. light brown sugar, ½ tsp. baking soda, ½ tsp. salt, ¾ c. salted butter
Assemble: Press ⅔ crumble firmly into pan’s bottom for a thick base. Spread filling evenly over crust. Sprinkle remaining ⅓ crumble loosely on top, letting some filling peek through.
Bake: Bake 25–30 min until topping is golden and filling bubbles. Cool in pan 1–2 hours before cutting into 9 squares.
Serve: Serve warm or at room temp. Store in fridge up to 4 days. Reheat gently if desired.

Thick Filling: Cook until jam-like to avoid excess liquid. Drain if needed before spreading.
Crisp Crust: Press crust firmly for a sturdy base. The cooked filling keeps it crisp.
Customize: Add ½ tsp cinnamon or ¼ cup chopped nuts for extra flavor.
Storage: Refrigerate for 4 days or freeze for 3 months. Thaw and reheat at 300°F for 10 min to revive crunch.