Oatmeal Cookie Cake with Brown Sugar and Cinnamon

Oatmeal cookie cake is a thick, chewy cookie baked in a round pan and sliced like a cake. Rolled oats, brown sugar, cinnamon, and chocolate chips give it familiar cookie flavor, while a short rest after baking helps the center set without losing its softness.

Ingredients

1 cup (125 g) all-purpose flour
1 teaspoon (5 g) baking soda
½ teaspoon (1.5 g) ground cinnamon
½ teaspoon (3 g) fine salt
½ cup (113 g) unsalted butter, softened
¾ cup (150 g) packed light brown sugar
¼ cup (50 g) granulated sugar
1 large egg (about 50 g without the shell), at room temperature
1 teaspoon (5 ml) vanilla extract
1½ cups (135 g) old-fashioned rolled oats
¾ cup (130 g) semisweet chocolate chips
⅓ cup (40 g) chopped walnuts or pecans (optional)
1 tablespoon (15 ml) milk, only if needed to bring the dough together
Flaky salt, for the top (optional)

Instructions

Heat the oven to 350°F (175°C). Grease a 9-inch (23 cm) round cake pan and line the bottom with a circle of parchment paper. The parchment makes it easier to lift out and slice the cookie cake; if you use a springform pan, set it on a baking sheet to catch any butter that might seep out.
In a medium bowl, whisk together the flour, baking soda, cinnamon, and salt. Set aside.
In a large bowl, beat the softened butter with the brown and granulated sugars for about 2 minutes, until creamy and evenly combined. A hand mixer makes this quick, but a sturdy spoon works too if the butter is soft.
Beat in the egg and vanilla until smooth, scraping down the bowl as needed. Add the flour mixture and stir just until no dry streaks remain. Fold in the oats, chocolate chips, and nuts, if using. The dough should be thick and scoopable. If it seems unusually crumbly and will not hold together when pressed, mix in the optional tablespoon of milk.
Press the dough evenly into the prepared pan, taking it all the way to the edges. Smooth the top without packing it down hard. If desired, sprinkle with a little flaky salt.
Bake for 22–26 minutes, rotating the pan once if your oven browns unevenly. The edges should look set and golden, while the center should be puffed and just set rather than wet or shiny. A toothpick may pick up melted chocolate, so check the dough itself near the center. Because the batter contains egg, the center should reach 160°F (71°C) for the USDA FSIS safe minimum for egg dishes; check with a food thermometer if unsure.
Cool in the pan for 15 minutes, then run a thin knife around the edge. Serve warm by the wedge, or let it cool completely in the pan for cleaner slices. Allow about 10 minutes to prepare ingredients, 5 minutes to mix and press the dough, 24 minutes to bake, and 10 minutes for the initial cooling before serving; the full 15-minute pan rest is included in the 49-minute total.

Tips

Measure flour by spooning it into the cup and leveling it, or weigh it. Scooping directly with the measuring cup can pack in extra flour and make the cookie cake dry or crumbly.
Use softened, not melted, butter. Melted butter can make the dough greasy and cause the edges to spread or fry before the center bakes through.
Old-fashioned rolled oats give the best chewy texture. Quick oats can work in the same quantity but make a softer, less distinct oat crumb; steel-cut oats are not a suitable substitute because they stay too firm.
For easier removal, cool the cake for the full 15 minutes and loosen the edges before lifting it out. The center will be tender while warm and firmer once fully cool.

Serving Suggestions

Cut the cookie cake into 10 wedges and serve warm or at room temperature. A scoop of vanilla ice cream, a spoonful of lightly sweetened whipped cream, or a glass of cold milk all pair well with the brown sugar and cinnamon. For a simple finish, dust the cooled top with a little powdered sugar or drizzle it with melted chocolate. If serving it warm with ice cream, plate the slices soon after cutting because the soft center can settle as it cools.

Variations

Swap the chocolate chips for the same amount of raisins, dried cranberries, or chopped dates for a more fruit-forward cookie cake. Chopped toasted pecans or walnuts add crunch; leave them out for a nut-free version, and check chocolate packaging if avoiding possible cross-contact. For a different flavor, replace the cinnamon with ½ teaspoon (1 g) ground nutmeg or add ½ teaspoon (1 g) finely grated orange zest. You can also use dark chocolate chunks instead of semisweet chips, keeping the quantity the same. Avoid adding a large amount of extra mix-ins, which can make the slices break apart.

Storage and Reheating

Cool the cookie cake, then cover the pan or transfer slices to an airtight container. Refrigerate within 2 hours of baking; it keeps for 3–4 days in the refrigerator. For the softest texture, bring a slice to room temperature or warm it briefly in the microwave in 10-second bursts. Reheat leftovers to 165°F (74°C) if reheating them for hot service, checking with a food thermometer. You can freeze well-wrapped slices for up to 2 months; thaw overnight in the refrigerator or at room temperature. Do not leave the cake uncovered at room temperature for longer than 2 hours.

Frequently Asked Questions

Can I make oatmeal cookie cake without a mixer?
Yes. Use a sturdy spoon to cream the softened butter and sugars until smooth, then stir in the egg and vanilla. Mixing by hand takes a little effort, but it works well as long as the butter is soft enough to combine easily.

Can I bake this in a different pan?
A 9-inch (23 cm) square pan works, though the pieces will be square rather than wedges. A 10-inch (25 cm) skillet may also work but can produce a thinner cookie, so begin checking a few minutes early. Pan material and depth affect baking time; look for set edges and a just-set center rather than relying on the clock alone.

Why did my cookie cake turn out dry?
Common causes are too much flour, overbaking, or using steel-cut oats. Weigh the flour if possible, remove the cake once the edges are golden and the center has just set, and use old-fashioned rolled oats for the intended chewy texture.

Can I make the dough ahead?
Yes. Cover the dough and refrigerate it for up to 24 hours. Let it sit at room temperature for about 20–30 minutes so it is easier to press into the pan, then bake as directed; a chilled dough may need a few extra minutes in the oven.

How do I know when the center is done?
The edges should be golden and firm, and the center should no longer look wet or glossy. The cake will continue to set as it rests. Since this is an egg-containing dish, the USDA FSIS safe minimum is 160°F (71°C); use a thermometer in the center if you need a precise check.

Can I make it without nuts?
Yes. Omit the nuts without replacing them, or add an equal amount of extra chocolate chips or dried fruit. The dough and bake time remain essentially the same.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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