Unsure about eggs, but they definitely have their own rotisserie chicken farm and plant.

Story goes that Tyson's chickens were becoming larger and larger and thus Tyson wanted more money.

Costco wants to keep the chicken at $5, so they starter their own plant.

They're commodity eggs in Costco packaging. They're even somewhat trackable; the USDA has databases[1] for this stuff.

So, for instance: The package of 24 large grade AA Kirkland-branded eggs from Costco that is in my fridge right now is stamped P3447. Plant 3447 is registered as being Daybreak Foods, 2127 110th Street, Otsego, Michigan (not Costco).

Milk is the same way: One can read the printing on the bottle and determine where it was processed.

[1]: The interface is genuinely awful, but: https://publicdashboards.dl.usda.gov/t/MRP_PUB/views/AMSLPQA...

> You can buy your eggs from Costco

If you live near a Costco, you can. The one near me is opening in a week, and I can't wait.

This isn’t really true. Their eggs are purchased from others (same as other Kirkland branding) and the chicken op for rotisserie is only a fraction.