From I-80: Take Emigrant Gap exit and travel 7 miles south east on Texas Hill Road 19.
Our favorite camping spot. Large spots with fire rings and picnic tables. Secluded with a remote feeling but not to far from the freeway.
It's a nice and clean camp ground. The only down fall is no water. Not horrible just more stuff to bring.
Camped here on July 4th weekend after originally aiming to camp at North Fork campground about a half mile down the road. We arrived late on July 3rd at North Fork and all of the walk-in sites were taken and the campground was slammed. Just up the road Onion Valley's sites (all walk-in / first come, first served) were wide open. A few people came late on the 4th, but still was pretty quiet. The swimming hole that draws the crowds to North Fork is easily accessible from Onion Valley. Fill up your water at the running spring fountain there too as there's no running water at Onion Valley. There are vault toilets, fire rings, and picnic tables though. Great spot overall.