We tent camped at this rustic park mid-week in August and had the entire place to ourselves! (Minus the cows). This park and lake are located about 20 miles East and South of Winnett, and state managed. Use is free, first come first served, I think. No cell service, and GPS got us a little lost getting there, but a local helped us out.
There are at least 7 dedicated sites there on the North side of the lake, that each are sort of "pull-though." They would be perhaps too small for anything larger than a teardrop or really short RV, and no power or water hookups. Each had a nice cement picnic table, and some tables had a really nice roof structure over them. I think every site had it's own fire ring. We found some fallen branches to burn, but otherwise no wood on site. There is a nearby primitive boat launch, and one pit toilet shared by all. I can't recall if there was a hand pump for water.
The reservoir was fairly low when we were there, and the site was by no means lush, but for a quick overnight it was perfect! Fish in the lake seemed active in jumping about. We read there are walleye, pike and perch. The rustic roads surrounding the lake were great for a walk and some night mountain biking. We also had some free range cows nervously come through the site, which was really novel to us Minnesotans. Proceed with Care - Cattle at Large!