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Blueberry Oatmeal Breakfast Bars

One oat mixture, used twice — pressed as a base and crumbled on top. Cut them cold or they fall apart.

Prep
20 min
Cook
40 min
Rest
2 hr
Makes
Makes 12 bars
Jump to the recipe
Toasted oat clusters spilling from a jar onto a board
Photo: Jess Loiterton / Pexels

One mixture does both jobs. Two-thirds gets pressed into the tin as a base, the rest gets crumbled over the fruit as a topping. It is less work than it sounds and there is nothing to balance between two competing textures.

Press the base firmly — really lean on it with the flat bottom of a glass. A loosely pressed base bakes into crumbs and the bars collapse when you lift them.

The blueberry layer needs cornstarch and lemon. Blueberries release a lot of liquid as they cook, and without a thickener that liquid soaks straight into the base and turns it to mush. The lemon is for balance: cooked blueberries are surprisingly flat on their own and the acid brings the flavor back.

The oat mixture is a close relative of the dough in oatmeal chocolate chip cookies.

Cool completely before cutting, and if you can, refrigerate for an hour first. Warm, the filling is molten and the base has not set; every bar tears. Cold, they cut cleanly and hold their shape for the rest of the week. This is the step people skip and then blame the recipe for.

A heap of rolled oats
Photo: Mondgesicht / Pixabay

Oatmeal breakfast bars: the card

One oat mixture, used twice — pressed as a base and crumbled on top. Cut them cold or they fall apart.

One oat mixture, one fruit layer

For the oat mixture

  • 3 cups (270 g) rolled oats
  • 1½ cups (190 g) all-purpose flour
  • ¾ cup (150 g) light brown sugar
  • 1 tsp ground cinnamon
  • ½ tsp fine salt
  • ½ tsp baking soda
  • ¾ cup (200 g) butter, melted
  • 1 tsp vanilla extract

For the blueberry layer

  • 3½ cups (500 g) blueberries, fresh or frozen
  • ⅓ cup (60 g) superfine sugar
  • 2 tbsp cornstarch
  • Juice and zest of 1 lemon

Pressing, filling and crumbling

  1. 1 Heat the oven to 350°F (175°C) convection and line a 23 × 33 cm tin with baking paper, leaving an overhang to lift the bars out later.
  2. 2 Mix the oats, flour, sugar, cinnamon, salt and baking soda. Stir in the melted butter and vanilla until the mixture clumps when squeezed.
  3. 3 Press two-thirds of it firmly into the tin. Use the base of a glass and press hard.
  4. 4 Toss the blueberries with the sugar, cornstarch, lemon juice and zest, and spread them over the base.
  5. 5 Crumble the remaining oat mixture over the top in loose clumps, leaving some fruit showing.
  6. 6 Bake 38–42 minutes, until the topping is golden and the filling bubbles at the edges.
  7. 7 Cool completely in the tin — at least 2 hours — then refrigerate an hour before lifting out and cutting.

Frozen fruit and keeping

  • Frozen blueberries work straight from the freezer. Do not thaw them; add 3 minutes to the bake.
  • They keep five days refrigerated and freeze well cut and wrapped individually.

Cutting healthy breakfast bars cleanly

Cut too warm. The filling sets as it cools and the base firms with it. Cool fully, chill an hour, then cut.