At Onion Valley, the "walk to" campsites are a short walk from the road that circles through the campground. You can drive your car close to unload, and then park your car at the central lot near the campground entrance (it is the dedicated campground lot, which is different from the much larger hiker/trailhead lot). While there are some drive-in lots that are nice for tents, the walk-tos are the nicer campsites in my opinion -- more in the trees.
We managed to jam two tents (one Fly Creek, one Hubba Hubba) into our site, but they are smaller sites.
