On the plant, the leaves of some varieties of marjoram look exactly like oregano; some of them even smell the same when fresh. Would you miss it if you omitted it? I've notice that a lot of recipes don't call for it at all.

I use about 1/2 oregano and 1/2 thyme when run out of marjoram.

Ditto pewins -- and if you have any thyme lying around, I'd add some of that as well because it has some of the same floral aroma that marjoram does.

use a little oregano...it's the same family