Oatmeal Chocolate Chip Cookie Cake

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I love an easy sheet cake, especially when it involves chocolate chips! And to top it all off, it tastes just like a fresh-baked oatmeal chocolate chip cookie! Can it get any better than that?

This recipe was inspired by a cake that I saw on Cake by Courtney’s Instagram account. With a few tweaks of my own, I came up with, what I believe is, the most perfect oatmeal chocolate chip cookie cake – it has the most amazing texture that, I assure you, makes this one of the best and most easy sheet cakes to make!

How to Make the Best Oatmeal Chocolate Chip Cookie Cake

If you’ve been following along with me for awhile now, you know that I live in Colorado and have really turned my baking into a science! Baked goods turn out much differently at elevations of 3,000 feet or above! If you are lower than this, feel free to skip over this section and go straight to the recipe below – just follow the instructions as is! But for those at higher elevations that really struggle to get the perfect cake, read on for my tips on how to make this oatmeal chocolate chip cookie cake your best sheet cake yet!

High Elevation Cake Adjustments

I made this sheet cake a few months back and let’s just say, it turned out less than perfect. Sunken and underbaked in the middle and chewy and over-baked on the edges. The cake portion stood all of about 2 inches tall. Not very fluffy and not very yummy either!

For this sheet cake, there is quite a bit of sugar in the recipe which can sometimes cause issues when baking at any elevation above 3,000 feet. According to King Arthur Flour’s High Altitude Baking Guide, “Increased evaporation also increases the concentration of sugar, which can weaken the structure of what you’re baking”. I believe that this was the main reason why my first attempt at this cake failed – it needed some adjustment on the sugar portion! I also did tweak a few of the other ingredients as well, which you can see below.

For reference, I live at 5,800 feet. These adjustments would likely give you the result that you are looking for if you live within a few hundred feet of where I am at. But high altitude baking can be a lot of trial and error. I’ll provide my explanations below for each adjustment I made. This should then give you a starting point to go off of to experiment with your own ingredients at whatever elevation you live at! I would also recommend checking out this guide here.

• Granulated Sugar – decrease by 1 tbsp. This should hold true at most high elevations. Always decrease your sugars by 1 tbsp. per cup.
• Brown Sugar – decrease by 1 tbsp. Same reasoning as for the granulated sugar.
• Flour – increase by 2 tbsp. Additional flour helps to strengthen the structure of the baked good so that it will rise correctly. At 3,500 feet, add 1 more tbsp. of flour per recipe. For each additional 1,500 feet, add one more tablespoon.
• Eggs – use 3 instead of 2. This will keep the baked good from drying out at a higher baking temperature and evaporation rate. If I am baking a cake, I like to add one more egg to increase the liquids in the recipe. This should hold true at most higher elevations, but experiment with it, of course!
• Baking Soda – decrease to 1/2 tsp. You can see this table on King Arthur’s website for how to adjust leavening agents for higher elevations (scroll down a ways to the “Leavening” section on their site). For my elevation, I typically cut all leavening agents in half. This allows for the right chemical reactions to happen between the other ingredients for the perfect rise. If there is too much leavening within the batter, not all of it gets used up (not all of it reacts with the other ingredients), so you are left over with a soapy bitter-tasting baked good due to the excess baking soda or baking powder in the batter.
• Increase oven temperature to 365° F. Since rising and evaporation proceed more quickly at higher elevations, you will want to use a higher baking temperature to set the structure of the baked goods so that they don’t sink in the middle and dry out on the edges. I recommend starting with increasing the baking temperature stated in the recipe by 15° F and go up from there in small increments (all the way up to 25° F increase if needed).
• Decrease baking time by 5 or more minutes. This is because you will be baking at a higher temperature. You don’t want your cake to burn! I usually decrease by 5-8 minutes per 30 minutes of baking time and adjust from there. Keep a close eye on your dessert in the oven while you are experimenting with time and baking temps.

If you have specific questions on high altitude adjustments, feel free to contact me and we can work them out!

Lastly, you will want to top this cake with some delicious frosting – vanilla would be yummy, but I recommend using this cookie butter frosting recipe below. It goes so well with this “cookie cake”! You can find cookie butter on Amazon or in your local grocery store (mine is always in the bread/bakery section!)

I hope that you enjoy this easy-peasy and delicious sheet cake!

If you’re looking for other cake recipes, check out my Cakes & Cupcakes page!

As always, be sure to tag me in your photos on Instagram if you make my recipe or use in your photos! I love to see what you are baking.