Why McDonald's Filet-O-Fish Only Comes With A Half-Slice Of Cheese

The Filet-O-Fish isn't the flashiest menu item at McDonald's. It doesn't have the double-decker style of a Big Mac and its buns are simple, unadorned by sesame seeds or a special eponymous sauce. But it's solid, simple, and delicious. Besides the plain bun, the sandwich consists of a mild-but-tasty fried pollock patty, a healthy helping of creamy tartar sauce, and a half-slice of cheese. But in that half-slice of cheese lies the humble mystique of the Filet-O-Fish. Every other sandwich on the McDonald's menu, if it includes cheese, has at least one whole piece. Why, then, did the chain's lone seafood offering get the short end of the slice? 

According to the McDonald's website, it's a matter of fidelity: "We go by the same Filet-O-Fish recipe one of our franchisees came up with way back when in 1961." If you'd like a whole slice of cheese, the site suggests requesting extra cheese. However, like that half-slice of cheese, this answer might leave you wanting more. After all, if the half-slice came from the original recipe, why did it only include a half-slice? There must be more to the story, and there is: Franchise owner Lou Groen's original recipe didn't include cheese at all. So when was cheese added, and why only a half-slice?

The story of the Filet-O-Fish is quite interesting. The sandwich first came about in 1961, when an Ohio franchise owner named Lou Groen came up with the sandwich as a way to feed Catholic customers during Lent. The original sandwich didn't much resemble the current iteration. For one thing, the original used halibut rather than pollock, and featured no cheese at all. It wasn't until the sandwich was released to McDonald's locations nationwide in 1965 that the sandwich took its current form with the iconic half-slice of cheese. Still, the question remains, why only a half-slice?

Over the years, McDonald's has offered up varying responses to inquiries. On X, McDonald's has responded to questions over the half-slice mystery by saying that the irregular portion was chosen in order to "...save on the flavor of the sandwich." But what does it mean to save on flavor? In 2012, the Canadian branch of McDonald's responded to the cheesy inquiry by saying that a half-slice of cheese is to maintain the balance between it, the tang of the tartar sauce, the crispness of the fillet coating, and the delicate flavor of the fish. So maybe it is just a matter of flavor, or perhaps it's simply tradition. We may never get a clear answer to this question; regardless, the half-slice has satisfied customers for over 50 years. Maybe they're on to something.