If you left bottled dressing on the counter by mistake overnight, toss or keep? Here's How Long Ranch Dressing Will Last Once Opened How Long An Open Bottle Of Ranch Lasts In The Fridge So I'm just learning ranch should be refrigerated. Otherwise don't eat it. I figured it had enough preservatives it would be OK out for a few days but Google says not to Here's How Long Ranch Dressing Will Last Once Opened