Thick and Chewy Chocolate Chip Oatmeal Cookie Bars

Why You’ll Love This Recipe

• Thick, bakery-style cookie bars that are soft and chewy all the way through.
• Loaded with hearty oats, caramel-y brown sugar, and big pockets of melty chocolate.
• No scooping individual cookies; everything bakes in one pan for easy prep and cleanup.
• Perfect for potlucks, lunchboxes, or freezing for future cravings.

Grocery List

• Produce: None
• Dairy: Unsalted butter, eggs
• Pantry: Light brown sugar, granulated sugar, all-purpose flour, baking soda, fine sea salt, ground cinnamon (optional), old-fashioned rolled oats, semisweet chocolate chips or chunks, flaky sea salt (optional)

Full Ingredients

For the Oatmeal Cookie Bar Dough

• 3/4 cup (170 g) unsalted butter, melted and slightly cooled
• 1 cup (200 g) packed light brown sugar
• 1/2 cup (100 g) granulated sugar
• 2 large eggs, at room temperature if possible
• 2 tsp pure vanilla extract
• 1 3/4 cups (220 g) all-purpose flour, spooned and leveled
• 1 tsp baking soda
• 3/4 tsp fine sea salt (or 1 tsp kosher salt)
• 1/2 tsp ground cinnamon (optional, but lovely with oats)
• 2 cups (180 g) old-fashioned rolled oats (not instant or steel-cut)
• 1 3/4 cups (300 g) semisweet chocolate chips or chopped chocolate chunks
• Optional: 1/2 cup (55 g) chopped toasted nuts (walnuts or pecans) for extra crunch

For the Pan and Finishing

• Nonstick baking spray or extra butter, for greasing
• Parchment paper, to line the pan
• Flaky sea salt, for sprinkling on top (optional but highly recommended)

Step-by-Step Instructions

Step 1: Prep the pan and preheat the oven

Preheat your oven to 350°F (175°C) with a rack in the center. Lightly grease a 9×13-inch metal baking pan with baking spray or a thin layer of butter. Line the bottom and two long sides with a sheet of parchment paper, leaving a couple of inches of overhang on the sides to use as handles later. This makes it much easier to lift the whole slab out for neat cutting.

If you are using a glass pan, you may need to bake on the longer side of the time range, as glass heats a bit differently than metal.

Step 2: Mix the butter and sugars

In a large mixing bowl, combine the melted, slightly cooled butter with the brown sugar and granulated sugar. Whisk or stir vigorously for 1–2 minutes, until the mixture looks thick, glossy, and well combined. The goal is to dissolve some of the sugar into the warm butter so the bars bake up chewy with a slight caramel note.

Make sure the butter is warm but not hot. If it is too hot, it can start to scramble the eggs in the next step, so let it sit for a few minutes if needed before adding the eggs.

Step 3: Add eggs and vanilla

Add the eggs and vanilla extract to the butter-sugar mixture. Whisk until the mixture turns lighter in color and slightly thickened, about 30–60 seconds. This helps create a smooth base that will hold the oats and chocolate without being greasy.

Scrape down the sides and bottom of the bowl with a rubber spatula to make sure everything is evenly mixed before adding the dry ingredients.

Step 4: Combine the dry ingredients

In a separate medium bowl, whisk together the flour, baking soda, fine sea salt, and ground cinnamon (if using). Make sure there are no visible clumps of baking soda or flour. This prevents any bitter spots and helps the bars rise evenly.

Pour the dry ingredients into the wet mixture. Using a spatula or wooden spoon, gently fold and stir just until you no longer see streaks of dry flour. The batter will be thick at this stage, which is exactly what you want for sturdy, chewy bars.

Step 5: Fold in oats and chocolate

Add the rolled oats to the bowl and fold them into the dough until evenly distributed. The dough will become quite thick and chunky. Next, fold in the semisweet chocolate chips or chunks and nuts, if using. Stir just until the mix-ins look well dispersed.

Do not overmix at this point; you want to keep the dough thick so the bars bake up dense and chewy, with big pockets of chocolate and oats in every bite.

Step 6: Press into pan and bake

Transfer the dough to your prepared 9×13-inch pan. Use a spatula or clean hands to press it evenly into the corners and edges, smoothing the top so it is as level as possible. Take a moment here; even thickness means the bars bake uniformly and avoid overdone edges.

If you like, sprinkle a light pinch of flaky sea salt over the top for a sweet-salty finish.

Bake for 22–28 minutes. Start checking at 22 minutes. The bars are done when the edges are deep golden brown, the top is lightly golden, and the center looks set but still slightly soft. A toothpick inserted near the center should come out with a few moist crumbs, not wet batter. Slight underbaking keeps them chewy instead of dry.

Step 7: Cool, slice, and serve

Remove the pan from the oven and place it on a wire rack. Let the cookie bars cool completely in the pan; this can take 1–2 hours but is worth the wait. Cooling allows the slab to set up so you get clean, sharp pieces instead of crumbling edges.

Once fully cooled, use the parchment overhang to lift the entire slab out of the pan onto a cutting board. Use a large, sharp knife to cut into 16 squares (4 rows by 4 rows) or smaller bite-sized rectangles if you prefer. Wipe the knife between cuts for the neatest edges. Enjoy at room temperature, or slightly warm individual bars for a few seconds in the microwave for extra melty chocolate.

Pro Tips

• Do not skip parchment: It makes removal, cooling, and cutting much easier and helps prevent overbrowned bottoms.
• Watch the center, not just the time: Pull the bars out when the center is just set with a little softness. Overbaking turns chewy bars into dry, crumbly ones.
• Use rolled oats only: Old-fashioned rolled oats give the best hearty, chewy texture. Instant or quick oats will make the bars denser and softer, and steel-cut oats will not soften enough.
• Mix in chocolate by hand: Folding in the chips or chunks manually keeps them from breaking up and ensures bigger chocolate pockets.
• Chill for ultra-neat slices: For picture-perfect squares, chill the baked slab in the fridge for 30–45 minutes after it reaches room temperature, then slice.

Variations

• Peanut butter swirl bars: Dollop 1/3 cup warmed peanut butter over the top of the pressed dough and gently swirl with a butter knife before baking. Use peanut butter chips in place of some of the chocolate if you like.
• Fruit and nut trail mix bars: Swap 1/2 cup of the chocolate chips for chopped dried cherries, cranberries, or apricots, and add 1/2 cup chopped toasted nuts for a trail mix vibe.
• Dark chocolate espresso bars: Replace 1/4 cup of the brown sugar with an extra 1/4 cup granulated sugar and add 1–2 tsp finely ground espresso powder to the dry ingredients, using dark chocolate chunks instead of semisweet.

Storage & Make-Ahead

Store the cooled cookie bars in an airtight container at room temperature for up to 4 days. To keep them extra soft, you can place a slice of sandwich bread or a piece of apple peel in the container; replace it every day or so as it dries out.

For longer storage, freeze individual bars tightly wrapped in plastic wrap, then placed in a freezer bag or airtight container, for up to 2 months. Thaw at room temperature for about 30 minutes, or warm gently in the microwave for 10–15 seconds. You can also make the dough up to 24 hours ahead: press it into the pan, cover tightly, refrigerate, then bake straight from the fridge, adding a few extra minutes to the baking time as needed.

Nutrition (per serving)

Approximate values for 1 of 16 bars: 260–290 calories; 14 g fat; 8 g saturated fat; 34 g carbohydrates; 2 g fiber; 20 g sugars; 4 g protein; 170 mg sodium. Actual nutrition will vary based on brands used, add-ins, and portion size.