We just spent one night at Cachuma Lake (a Sunday), camping near Chumash Meadows. The tent camping sites were probably only ~30% full, which made for a very peaceful (albeit short) stay! The sites are big with picnic tables and fire pits, and many are shaded by large trees. The nearby toilet block was clean, as were the showers (a little further away). Our tent site had a view out to the lake, and was a bargain! 

There is a store (with a not-so-great assortment of goods), a restaurant and a fishing/boat hire shop. The roads and paths make for great cycling, and there are trails to explore too.

We drove through the whole camp ground checking out the various areas (full RV sites, partial RV sites, tent sites, yurts & cabins). The full RV sites were (not surprisingly) still pretty full, even in mid-October, but the rest were not. We loved the campground, and plan to return for longer next time. Its proximity to cute little nearby towns is a bonus!