We Tasted Costco's Kirkland Signature Grass-Fed Butter And It Gives Kerrygold A Run For Its Money

Whether you're a baker, cook, butter-board enthusiast, or someone who simply enjoys the occasional slice of toast, butter is likely a staple in your refrigerator. The next time you stroll through the refrigerated aisles of Costco, you'll notice a recently launched contender among the salted butter options: Kirkland Signature Grass-Fed Butter. Many people can taste the difference between grass-fed and regular butter, but how does one grass-fed butter stack up against another?

Curious, I decided to test Costco's grass-fed butter against Kerrygold Irish butter — widely considered the gold standard of grass-fed butter — in a head-to-head showdown. I evaluated both butters for taste, color, texture, and price to determine which one reigns supreme. To ensure a fair comparison, for both brands I arranged to leave the butter out at room temperature and conduct a blind taste test of them on their own, as well as spread on cream crackers.

Growing up, I regularly enjoyed cream crackers slathered with butter, so it's a familiar and beloved combination for me. These savory crackers are made with wheat flour, oil, and yeast, and have a plain flavor that provides the perfect canvas for showcasing the richness of butter. My appreciation for butter grew as I embarked on a career as a cookbook author and pastry chef, emphasizing the importance of using high-quality butter in cooking. Read on to discover if Costco's grass-fed butter is good enough to dethrone Kerrygold, and earn a spot in your shopping cart.

Available since 2021, Kirkland Signature Grass-Fed Butter is a premium offering from Costco's private label, sold exclusively at the chain's big-box stores or on its website. The butter is made from the milk of cows that graze on New Zealand's lush green pastures. The milk is sourced from some 400 farms, where cows consume a diet of at least 95% grass, along with supplemental grain feed that is GMO-free, adhering to New Zealand's strict bans on GMOs and growth hormones in dairy farming. 

To produce its grass-fed butter, Costco partnered with New Zealand's Westland Milk Products, based in the South Island town of Hokitika. Westland boasts a rich butter-making tradition, with its roots intertwined amid the region's dairy-industry history dating back over 150 years. 

Beyond offering rich flavor, Costco's grass-fed butter has potential health benefits when eaten in moderation. It is a natural source of vitamin A and contains considerable levels of conjugated linoleic acid, which is a fatty acid that may help reduce body fat and build muscle mass.

Costco sells Kirkland Signature Grass-Fed Butter at its U.S. locations. I found it in the refrigerated section of my local store near the cheese — and there was plenty of it. Still, it's always a good idea to call your usual Costco location before visiting to see if it's in stock.

Kirkland Signature Grass-Fed Butter is sold in a shiny green box that includes four 8-ounce bars of butter (for a total equal to eight American sticks of butter). I paid $9.99 for a box, which computes to about $2.50 for 1 cup of butter (or two American sticks). 

Kerrygold is regarded as the best butter brand, and it's also sold by Costco in a package of four 8-ounce bars of butter. I paid $14.49 for the box, which computes to just over $3.62 for 1 cup of butter. So, if you purchase Costco's grass-fed butter instead of Kerrygold, you'll save $4.50 in total and more than $1 per cup of butter. 

The ingredient list for Kirkland Signature Grass-Fed Butter is short: "Pasteurized cream (milk), salt." A single tablespoon of this butter contains 100 calories, 11 grams of fat, and 30 milligrams of cholesterol. It contains 75 milligrams of sodium, which is notably lower than many other salted butters on the market; for comparison, Land O Lakes, Challenge, and Plugrà each contain 90 milligrams of sodium per tablespoon. Kirkland Signature Grass-Fed Butter also has no carbs or protein.

Kerrygold's ingredients are similarly straightforward: "Pasteurized cream, salt." Each tablespoon of butter provides the same 100 calories, 11 grams of fat, and 30 milligrams of cholesterol. However, this butter contains 100 milligrams of sodium per serving, which is 25 more than what's found in Costco's grass-fed butter. Similar to the Kirkland Signature product, Kerrygold also has zero carbs and protein.

Both Kirkland Signature and Kerrygold butter should be stored in the refrigerator to maintain their freshness. Their best-by dates were about 10 months after the purchase date. 

Removing the shiny green foil from Kirkland Signature Grass-Fed Butter is like unwrapping a bar of gold. Its striking yellow hue is nothing short of stunning, and its thick, creamy texture screams decadence. When tasted on its own, the butter offers a subtle-yet-delightful buttery taste that truly shines when spread on a cream cracker. While the butter's thick consistency makes it slightly challenging to spread cleanly, it leaves a coating on the tongue that some may enjoy.

Kerrygold's salted butter, in contrast, has a more pale shade of yellow, but it's equally attractive. Its texture is soft and ultra-smooth, melting instantly upon touching the tongue for a luxuriously creamy experience. The initial taste of rich butter is followed by a hit of saltiness, which some may find overpowering. However, when enjoyed on a cream cracker, all the flavors are balanced, with even a hint of sweetness shining through. The butter's soft texture makes it effortless to spread and incredibly satisfying. 

Both Kirkland Signature Grass-Fed Butter and Kerrygold's salted butter are delicious, with only slight differences. Costco's version is a New Zealand product, while Kerrygold hails from Ireland. The other difference is salt content. Salt is an important ingredient that enhances the flavor of food, and it can elevate a dish from "meh" to tasty with just a pinch. The high salt content in Kerrygold's butter gives it punch, like adding a splash of acidic flavoring to enhance the taste of a dish. However, Kerrygold's hit of saltiness may be too intense for those sensitive to salty foods. 

Deciding between the butters may come down to usage. Kerrygold would be a joy to spread on a butter board, and its salty taste would complement various toppings. Other applications would work well, like using it in mashed potatoes, making it into compound butter, or baking it into a pound cake. 

On the other hand, Costco's Kirkland Signature butter, with its lower salt content and prominent butter flavor, would elevate cooked dishes to gourmet levels with its rich flavor profile. It would be great for finishing a sauce, or for more involved cooking like sautéing veggies, butter-poaching lobster, and pan-searing steak. 

If you're searching for a delicious grass-fed butter, try the Kirkland Signature variety. While its waxy consistency may not be desirable when eaten as a spread, it's perfect for cooking, when the texture won't cause any concern. And at about $2.50 per cup, Costco's grass-fed butter is a money-saver compared to Kerrygold. 

Ultimately, your choice might come down to whether you're ready to stock up on 32 ounces of butter at one time. But if that's not an issue, you'll be satisfied with Kirkland Signature Grass-Fed Butter — it's a versatile, well-priced option for gourmet-level butter.

This taste test made me realize that I rarely buy salted butter. I primarily use butter for baking, so unsalted butter is my preferred choice. When serving dinner rolls, I usually opt for unsalted butter sprinkled with flaky sea salt, and I often splurge on unsalted Kerrygold butter for special occasions, or when hosting guests. However, if Costco ever decides to offer an unsalted version of their grass-fed butter, that's the one you'll find in my shopping cart.