[thoughtexprmnt]

Two things to look for when selecting olive oil at the supermarket - a dark glass bottle, and a harvest date printed on the label. Granted, this doesn't guarantee you're getting a high-quality, non-blended EV olive oil, but without these you most assuredly are not.

[bluGill]

Don't go to a supermarket to get good olive oil in the US. There are a few small stores scattered around that sell good olive oil.

Dark glass is cheap and so cheap oil at a premium price comes in a fancy dark bottle. You are paying for the fancy bottle (which doesn't cost much more than a cheap plastic bottle of the same stuff - profit)

A harvest date is useful if you can find one, but doesn't really mean quality. If the date is more than 3 months ago it means subpar though which is something.

[deadmetheny]

This isn't strictly true - you can get good, real extra virgin olive oil at, say, Whole Foods, but it's gonna be from California. Tinted glass keeps UV light from degrading the product, similarly to why no decent beers come in clear glass.

You're completely correct about getting good imported olive oil from a supermarket though, absolutely.

[Doxin]

The main thing about the dark glass bottle is that UV damages olive oil making it taste worse. If your olive oil is in a container that lets in UV you're guaranteed that the manufacturer doesn't give half a hoot about quality.

[divbyzer0]

By far the best indicator of quality I have found is the acidity level. The higher acidity oils tend to omit this detail in packaging. I aim for 0.3%.

The higher quality olive oils have been sold in 'tin-cans', but that alone does not indicate quality.