This 6-ingredient oatmeal cake is one of those cozy, old-fashioned desserts that feels like it came straight from a church potluck or a grandma’s recipe box. It bakes up in the same pan you mix it in, and you frost it right there too—no fussing with layers or fancy decorating. The oatmeal gives it a soft, comforting texture and a homey flavor that makes the whole kitchen smell like a hug. It’s the kind of cake you make on a Sunday afternoon when you want something warm and simple to share with your family, or when you need a quick dessert for a neighbor or school event without a long ingredient list.
This oatmeal cake is lovely served just slightly warm so the frosting stays soft and a little gooey. It pairs beautifully with a glass of cold milk for the kids or a cup of coffee or tea for the grown-ups. If you want to stretch it into a more special dessert, add a scoop of vanilla ice cream or a dollop of lightly sweetened whipped cream on the side. For a brunch table, you can cut it into smaller squares and serve it alongside fresh fruit, scrambled eggs, and sausage or bacon. It also packs well in lunchboxes—just cut into squares, wrap tightly, and tuck in with some apple slices or baby carrots for a balanced little treat.

 

6-Ingredient Oatmeal Cake (Frosted in the Pan)
Servings: 9–12 servings

Ingredients
1 cup quick oats (or old-fashioned oats)
1 cup milk
1 box (about 15.25 oz) yellow cake mix
1/2 cup vegetable oil (or canola oil)
3 large eggs
1 tub (about 16 oz) prepared cream cheese frosting (or vanilla frosting)
Directions
Preheat your oven to 350°F (175°C). Lightly grease a 9×13-inch baking pan with cooking spray or a thin layer of oil.
In a medium bowl, stir together the oats and milk. Let this mixture sit for about 5–10 minutes so the oats can soften. This gives the cake a tender, cozy texture.
In a large bowl, add the dry cake mix, vegetable oil, and eggs. Beat with a hand mixer or whisk well until smooth and no dry streaks remain.
Stir the softened oat-and-milk mixture into the cake batter until everything is well combined. The batter will be a bit thicker than a regular cake batter, and that’s okay.
Pour the batter into the prepared 9×13-inch pan and spread it into an even layer with a spatula.
Bake for 25–32 minutes, or until the top is golden and a toothpick inserted in the center comes out clean or with just a few moist crumbs. Ovens vary, so start checking around 25 minutes.
Set the pan on a cooling rack and let the cake cool until it is just barely warm to the touch, about 30–40 minutes. If it’s too hot, the frosting will melt; if it’s completely cool, the frosting will still spread fine but won’t sink in as cozily.
Once the cake is slightly warm or cooled, spread the cream cheese frosting evenly over the top, right in the pan. Use the back of a spoon or an offset spatula to make soft swirls.
Let the frosted cake sit for at least 15 minutes so the frosting can settle. Slice into squares and serve straight from the pan. Store leftovers covered at room temperature for up to 2 days, or in the refrigerator for a slightly firmer, cheesecake-like frosting texture.

Variations & Tips
For picky eaters, you can use vanilla frosting instead of cream cheese if they prefer a milder flavor, or even chocolate frosting for a more dessert-like feel. If your family loves texture, stir in a small handful of mini chocolate chips or butterscotch chips to the batter before baking (this will add an extra ingredient, but it’s worth it for a fun twist). For a lightly spiced version, sprinkle ground cinnamon over the frosted cake or add a teaspoon of cinnamon to the batter when you mix in the oats. To make it feel a bit more wholesome for breakfast or brunch, you can reduce the frosting and just spread a thin layer, then top with sliced strawberries or blueberries right before serving. If you need to plan ahead, bake the cake the night before, cover it tightly once it cools, and frost it the next day—this can actually make the texture even better. For smaller households, cut the cooled cake into squares, wrap individually, and freeze; thaw at room temperature and add a thin smear of fresh frosting when you’re ready to serve for a quick, homemade treat on busy weeknights.