Costco is very good, and the last time I checked, I believer Consumer Reports ranked Trader Joe at the top. You probably can't go wrong with either.
The OO industry is the Wild West, w/ no regulation national or int'natl. Notably exposed in this NPR piece. Caveat emptor!
Trader Joe's California Estate gets high marks here. Recently bought a bottle but haven't opened it yet.
Can you use any olive oil for cooking? I know some of them break down fast under high heat...........