jQuery CSS 'or' selector

I am trying to select elements of a (certain class || another class) with the same selector. How can I go about doing that?

Currently, I have:

$(".class1 .class2").each(function(idx, el) {... });

however, that only selects elements that match both classes, not one or the other.

How can I select elements that match one or both of the classes, with the same selector?