bare minimum: feta cheese and olives.
Down in the Palmetto Flat, river, and jungle of Florida they serve a Greek Salad like I have never seen. They place a big old scoop of sweet mustard tater salad in a salad plate and build a classic American “Greek Salad” around it. It’s pretty damn good.
This is what I had in Greece.
This is what I typically get in the States, but quite often, cucumbers are included.
I have a vinaigrette recipe from a Greek-American friend, and it is just as Drain Bead says: heavy on oregano and lemon.
This is what i usually get (in Europe, but not Greece perse). i have never ever seen tomatoes or cucumbers in greek salads.
To be fair, every Greek salad I’ve ever had in Greece has been called ‘Greek salad’ on the menu, but I imagine this is down to being in tourist areas (Greek islands, specifically).
This, too, is what I’ve already had in Greece. Onions are either red or white.
In the Detroit area, beets are a necessary component. Why we’re the only ones who do this, I’ve no idea, but I love them that way.
So, greens with kalamata olives, beets, feta, pepperocini, cucumbers and tomatoes is a standard greek salad to me. Often, bell peppers and chick peas are included. Dressings range from the typical vinaigrettes with lemon and herbs to some sort of thickish creamy pink stuff of unknown origin.
ETA: red onions are also standard, but I prefer to order without.
Romaine lettuce with tomatoes, cucumber, red onion, olives, feta, an oil-and-vinegar dressing, and oregano. Bonus points for having roasted red peppers too.
I’ve had this, with olives, beets and anchovies and enjoyed it a lot.
Yet nobody expects greens in a caprese salad.
Was in Greece less than a month ago and I have pictures of two salads that were divine!
I’ll take either, please.
I’ve seen it with arugula, but I know that’s not really Insalata Caprese (though I enjoy it quite a bit.)
I suppose the basil leaves, in their aromatic way, serve as the greens.
I never heard of beets in a Greek salad, but then I remember the first time, many years ago, when I tried chicken/spinach enchiladas–and liked 'em.
I’m in the Midwest. Asking for “horiatiki” will cause confusion 
It was a Greek salad from Detroit that had beets, prompting the OP.
I expect a Greek salad to be a salad that I don’t need to specify anything, including the dressing.
Romaine lettuce, tomato, cucumber, red onion, Kalamata olives, feta cheese, and a dressing of olive oil, lemon juice or vinegar, salt and pepper.
And the verdict?
C’mon, admit it, it was good wasn’t it? Pickled beets making your feta all pinkish and extra yummy. Give in to the weirdness!
My personal experience with Greek salad (from having a best friend who is Greek) is there is no lettuce…and the onions were always pulled from the wild onions growing in the yard (in South Carolina)…Here in Omaha…order Greek salad and you get the traditional salad with no greens. If you want greens, you order the “Athenian” salad…both are spectacularly good and look like the photos taken by “Sleeps with Butterflies”.
I’ve had greek salads with beets. Very specifically the crinkles cut, cubed, canned and pickled, sweet and sour beets. That was local and it wasn’t detroit. It was at a lebanese place with their version of “mediterraneaen salad.”
When I make it:
Feta, cucumber,onion, kalamata olives, tomatoes, oregano, grilled slices of lemon, olive oil, with pieces of toasted pitta, taramasalata and tzatziki on the side and served with nice grilled lamb chops in the summer.
I don’t like green capsicum/peppers so I don’t add them.
I also do a “Cypriot” version with grilled Halloumi instead of feta if I’m not serving lamb.
I have spent a fair amount of time on Crete. There, the village salad is tomatoes, cucumber, onion, oregano, olive oil and lemon juice. Feta and olives were present but always on the side.