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Chocolate Chip Oatmeal Cookie Bars — One-Bowl, No Mixer Dessert Pinterest recipe pin

Chocolate Chip Oatmeal Cookie Bars

One-bowl chocolate chip oatmeal cookie bars baked in an 8×8 pan for chewy, sliceable bars—no mixer required and pantry-friendly ingredients.
Print Recipe Pin Recipe
Prep Time 15 minutes
Cook Time 25 minutes
Total Time 40 minutes
Servings: 9 bars
Calories: 280
Ingredients Equipment Method Notes

Ingredients
  

  • 1/2 cup 1 stick unsalted butter, melted and slightly cooled
  • 1 cup packed light brown sugar
  • 1/2 cup granulated sugar
  • 1 large egg room temperature
  • 1 teaspoon vanilla extract
  • 1 cup old-fashioned rolled oats
  • 3/4 cup all-purpose flour
  • 1 tablespoon cornstarch
  • 1/2 teaspoon baking soda
  • 1/2 teaspoon fine sea salt
  • 3/4 cup semisweet chocolate chips
  • Optional: 1 tablespoon milk only if batter seems dry
Optional toppings
  • Flaky sea salt for sprinkling optional

Equipment

  • 1 8×8-inch baking pan
  • 1 Large mixing bowl
  • 1 Parchment paper
  • 1 Rubber spatula

Method
 

Prepare the pan and oven
  1. Preheat the oven to 350°F and line an 8×8-inch pan with parchment paper leaving an overhang or grease the pan well.
Mix wet ingredients
  1. In a large bowl, combine the packed brown sugar and granulated sugar, then stir in the melted butter until glossy; add the egg and vanilla and mix until smooth.
Add dry ingredients
  1. Stir in the rolled oats, flour, cornstarch, baking soda, and salt until just combined, then fold in the chocolate chips; add up to 1 tablespoon milk only if the batter is noticeably dry.
Bake
  1. Press the batter evenly into the prepared pan, bake at 350°F for 20–26 minutes until edges are golden and a toothpick inserted near the center comes out with moist crumbs (not raw batter); if using a glass pan, aim for the upper range of time.
Cool and slice
  1. Cool the pan on a wire rack for 25–35 minutes so the bars set, then lift the slab out using the parchment overhang and slice into 9 bars; sprinkle with flaky sea salt if desired.

Notes

Use old-fashioned rolled oats for the best texture; quick oats yield softer bars. If you prefer chunkier chocolate, chop a chocolate bar instead of using chips. Letting the bars cool in the pan for at least 25 minutes is essential to prevent crumbling when slicing.