Butter vs. Oil for Baking—Here's Which Fat Makes the Best Cookies, Cornbread, and Cake

Baking is often considered a science. Many ingredients trigger chemical reactions that shape the final texture and flavor of what comes out of the oven. Most baked goods rely on just a handful of basic ingredients—flour, a leavener, sugar, eggs, and some form of fat—combined in various ratios depending on the desired result; even small changes can make a big difference. You can't simply make chocolate chip cookies with half the flour or swap powdered sugar for granulated and expect consistent results. Still, there's room for experimentation, and one of the most common tweaks bakers make is switching between butter and oil. But knowing when and how to make that swap is more complicated.

Butter and oil both provide the fat that gives baked goods their tender crumb, moist texture, and rich flavor—but they don't behave the same way. The fat you choose can dramatically affect not only texture but also flavor and freshness in everything from cookies to cornbread to cake. So what really happens when you swap oil for butter, or vice versa, in a recipe? To find out, I tested three classic recipes—sugar cookies, cornbread, and cupcakes—to see how the type and state of fat can influence the results. My goal was to gain a better understanding of when the choice of fat truly matters, and to show when you can more confidently substitute one for the other, and when you can't.

A Quick Word About Fats

Fat provides tenderness, moisture, and richness—it's a big part of what keeps baked goods soft rather than tough, flavorful rather than flat. If you've ever forgotten to add fat to cookies, pancakes, or muffins, you'll know immediately that something's missing. The results will be dense and disappointingly dry. In some recipes, swapping butter and oil can throw off the final product in subtle yet noticeable ways.

"When you compare butter and oil in baking, the key differences come down to fat composition, water content, and how each behaves when mixed and heated," explains Jessica Gavin, a certified food scientist. "Butter is about 80% fat and 16% water, so it melts quickly, spreads more in cookies, and adds just enough moisture to activate gluten."

Butter is classified as a saturated fat because it remains solid at room temperature. "Because it's solid at room temperature, you can cream it with sugar to trap tiny air bubbles," Gavin says. "This gives cakes their rise and that soft, melt-in-your-mouth crumb. Butter's butyric acid and milk solids also contribute rich flavor and beautiful browning."

Most cooking oils—such as vegetable, canola, or olive oil—are "100% unsaturated fat, so [they] don't aerate the same way," explains Gavin. "The crumb tends to be a little spongier, but it stays incredibly moist. Since oil remains liquid at room temperature, it bonds with starch and slows retrogradation, the natural staling process. That's why oil-based cakes stay tender longer, while all-butter cakes can feel drier the next day."

Testing Parameters

To get a clear sense of how butter and oil behave across different baked goods, I tested three recipes that represent distinct fat applications:

• One that uses creamed butter in its original recipe (sugar cookies)
• One that calls for melted butter (cornbread)
• One that starts with oil (yellow cake mix cupcakes)

This setup allowed me to compare fats as they were initially intended to be used, while also seeing how each performed when swapped. It made it easier to isolate how the fat's state (solid vs. liquid) and composition (saturated vs. unsaturated) affect structure, texture, and flavor across different baking styles.

The Sugar Cookies Test

I started with a recipe that relies on creamed butter, a technique common to many cookie recipes in which butter is beaten with sugar until well aerated, leading to a lighter, fluffier texture. This test compared creamed butter with oil, which can't be creamed in the same way. This way, we could see how the creaming stage affects the final cookie.

I used a basic drop sugar cookie recipe made with all-purpose flour, baking powder, salt, granulated sugar, egg, vanilla, and room-temperature unsalted butter. The softened butter was creamed with the sugar to create a light and airy base for the wet ingredients (the egg and vanilla). The dry ingredients were then gently stirred in, and the dough was portioned, rolled into balls, and refrigerated for 15 minutes before baking. The final cookies had all the qualities I love in a drop cookie: soft and chewy centers, slightly crisp edges, and a rich, buttery flavor.

For the next batch, I swapped the softened butter with vegetable oil. While it's generally recommended to adjust recipes when switching between butter and oil—because butter contains added water—I didn't reduce the oil in this case. I wanted to start by seeing if an easy 1:1 swap would work. I beat the sugar and oil together just as I had in the first test, but the mixture never became light and fluffy (not exactly a surprise). I then proceeded with the recipe as described above.

One striking difference appeared before baking: The fully mixed oil-based batter was noticeably smoother than the butter-based version, but didn't hold its rounded shape as well when rolled. Once baked, though, the cookies with oil turned out fine, though there were noticeable differences. The main differences were a crisper, less chewy texture and a more subdued flavor.

That's likely because butter gives cookies their quintessential rich, buttery flavor. Vegetable oil, by contrast, has a neutral taste and doesn't contribute as much flavor, as expected. A robust olive oil might lend a more floral note, but without some kind of flavorful fat, such simple cookies taste flat. As for texture, creaming softened butter with sugar creates tiny air pockets that expand during baking as the butter's water evaporates, yielding a pleasantly light, tender crumb. The same aeration of fat didn't occur when I beat together the oil and sugar. The consistency of the oil and sugar mixed together was smooth and uniform. Once baked, it was clear the oil-based cookie's missing element was aeration, which you achieve when creaming together butter and sugar. The oil-based cookies had a more crisp, uniform texture once baked, and they lacked that chewy bite that makes butter-based cookies so delicious. 

While I clearly prefer the texture and flavor of butter-based cookies in this context, I was pleasantly surprised by how well the oil-based version turned out. It's a decent option when you're craving freshly baked cookies but don't have butter on hand—just don't expect a cakey, aerated texture or rich, buttery flavor in the finished cookie.

The Cornbread Test

Next, I moved on to a recipe that uses melted butter, allowing me to compare it directly with oil—two fats that, when in their liquid state, behave similarly during mixing but differ once baked.

I followed a straightforward cornbread recipe made with cornmeal, buttermilk, baking powder, baking soda, salt, all-purpose flour, sugar, eggs, and melted butter. The ingredients were gently combined and poured into an 8-inch square baking dish. Once baked and slightly cooled, the buttery cornbread was rich, fairly light, and quite tender. Notably, I avoided browning the butter to retain its water content and keep the milk proteins from toasting.

For the next test, I swapped the melted butter with vegetable oil. The oil-based cornbread was similar to the butter version but with a few key differences. First, it didn't brown as well—likely due to the absence of milk proteins. It also lacked the buttery richness expected. However, the texture was slightly lighter and more moist. That could be due to oil's higher fat content, but more likely it's because oil is mostly unsaturated. Even after baking, oil retains its liquid character, while butter tends to solidify, resulting in a denser, firmer crumb. My preference? I could go either way, since the differences were mild—but I did prefer the richer flavor of the butter-based version.

The Cupcakes Test

Finally, I tested a recipe that starts with oil to see how well melted butter performs when swapped in.

I used a boxed yellow cake mix for this test—not because I needed a shortcut, but because it provided a neutral, consistent base to evaluate fat swaps without other variables like ingredient ratios or mixing methods. This particular brand included a flour blend of wheat flour, potato starch, and potato flour, along with sugar, baking powder, and sea salt. I specifically chose a mix without a lot of additional processed ingredients. The package instructions called for oil, so in the first test I followed the standard recipe. For the second test, I substituted melted and cooled butter for the oil.

The differences here were also relatively minor, and both versions produced surprisingly delicious cupcakes. Each was moist and fairly airy, but the oil-based batch had an edge thanks to its exceptionally light, tender texture. Again, that's likely because butter, being saturated, tends to solidify as it cools. This was especially noticeable after I refrigerated the cupcakes overnight: the ones made with melted butter turned dense, while the oil-based cupcakes stayed moist and tender.

Of course, the butter-based cupcakes were richer—but in this case, that's not necessarily ideal. The oil-based version was pleasantly sweet with a light, airy crumb that paired beautifully with a swipe of sweet frosting on top.

Final Verdict

As a general rule, you can use melted butter and oil interchangeably in most recipes that call for either. Melted butter adds richness and promotes browning, thanks to its milk proteins, while oil's unsaturated fat content helps baked goods stay lighter and moister. If substituting oil for melted butter, it's a good idea to reduce the amount by about 15% to account for butter's water content, which cooks off during baking.

The more significant differences arise in baked goods that rely on creaming. Sugar and oil simply don't cream together the way softened butter and sugar do—and that process is key to developing a chewy crumb with slightly crisp edges. Using oil in recipes that call for creamed butter results in a denser, crunchier texture. It can work in a pinch, but the outcome is generally less desirable and certainly not what the recipe intended.

In short, there's no universal winner. Butter brings deep flavor and beautiful browning; oil delivers superior tenderness and moisture retention. The trick is matching the fat to the method—cream butter when you want structure and flavor, use oil when you want lasting softness.