Why This Costco Protein Item Is Frequently Returned

We may receive a commission on purchases made from links.

When making a Costco run and browsing the store's veritable treasure trove of bulk goodies, you'll find some ridiculously expensive Costco groceries (some worth the premium price and others not), some must-have bargains under $5, and lots of products that fall somewhere in between. Whichever end of the spectrum your favorites land on, we definitely love our Costco finds. But not everything from the big-box warehouse store is worth taking home — which is why some products end up getting returned ... like, a lot. One such product is the chain's Kirkland Signature Protein Bars, which are among Costco foods shoppers return the most.

While, generally speaking, opting for Kirkland Signature products — Costco's private label brand — is one of the best Costco food shopping tips, many shoppers have found the protein bars to be an exception. Complaints about the bars range from inconsistency in quality and taste from one batch to another to hard-as-a-brick textures, tasting artificial and overly sugary, leaving a chemical aftertaste, and being just downright inedible. Some users have pointed a finger at apparent recipe changes that resulted in reduced size and diminished quality, turning former fans of the products into now-disgruntled patrons who have boxes of untouched bars sitting on their pantry shelves. One creative buyer on the Costco product page suggested letting kids use the inedible bars as toys or to hang them outside for birds.

The more practical thing to do, of course, is return the products, which countless patrons have done. The complaints span years, though, which begs a question some critical customers have voiced: Why is Costco selling a product that has prompted so many complaints and returns? The chain is usually very selective about the goods it sells under the Kirkland Signature label.

We don't know exactly why Costco has continued vending the Kirkland Signature protein bars in spite of mountainous complaints and myriad returns. Hundreds of negative comments about the bars are posted on the company's product pages, and the variety pack containing Chocolate Peanut Butter Chunk and Cookies and Cream is rated only 3.7 out of 5 stars on Costco's website, as of January 2026. Buyer complaints go beyond merely disliking the bars, too. In addition to grievances about taste and texture, various users have reported digestive issues from eating Kirkland Signature protein bars, with stated symptoms ranging from increased flatulence to stomach cramping and diarrhea. The bars contain erythritol, which is known to cause stomach upset.

The Kirkland Signature protein bars include Chocolate Chip Cookie Dough, Chocolate Brownie, Chocolate Peanut Butter Chunk, and Cookies and Cream flavors that offer between 21 and 22 grams of protein per bar. There is also a chewy protein bar variety that has 10 grams of protein per bar. As of January 2026, the chewy protein bars were offered in a Peanut Butter & Semisweet Chocolate Chip flavor only.

Both types of Kirkland Signature protein bars have received criticism from purchasers, but the bulk of the chewy reviews are positive. While the majority of the backlash is leveled at the non-chewy bars, reviewers on the Costco website have pointed out that the chewy bars contain bioengineered ingredients, aka GMOs (with the fact obscured in product descriptions and printed in tiny letters on the packaging, so it's difficult to see). Others have called out the chewy bars for being overly sweet and more like a candy bar than anything else.

Emerging from all the customer complaints regarding Costco's Kirkland Signature protein bars, one particular flavor stands out as the very worst of the worst: Cookies and Cream. From the product page on the Costco website to Reddit threads and many sites in between, complainants call out the Cookies and Cream flavor again and again, calling it outright inedible and the worst protein bar they've ever had. Trying to eat the Cookies and Cream bars is like biting into a rock, a few noted, while others commented that microwaving is required just to make them edible. The texture is grainy, hard, and dry, and the only flavor is an aftertaste, a customer stated on the Costco product page. Among the many who have returned these specific bars to the stores from whence they came, one product-returning Redditor compared the taste of the Cookies and Cream flavor to "spit up milk."

Another common complaint appears in tandem with buyers opining the flavor and texture woes of Cookies and Cream: The non-chewy Kirkland Signature protein bars are no longer available in standalone flavors. One has to purchase combo boxes. This means that in order to get a flavor they like, purchasers have to also buy a large number of other flavors they don't like — such as Cookies and Cream (though Cookie Dough is a definite runner-up for user dislike). In order to get a one-flavor-only box, customers report turning to other purchasing sites outside of Costco. Amazon, for instance, carries single-flavor boxes, and Costco Business Center locations reportedly sometimes have the one-flavor options, too (as of January 2026, the Costco Business Center website offered just the Chocolate Chip Cookie Dough flavor as a standalone option).