If you want big trout, there are a number of lakes that I know have some real biggies, and they are not going to be hurt by pressure from what I can see. Roosevelt has some pigs plus huge (my standards) kokanee. Banks has big fish, and so does the Potholes and Moses. These last get fished pretty hard, so you're not going to have a high chance of a really big fish, but there will likely be a number of trout over two or three pounds you'll catch with the chance of something big.

There are some smaller bodies of water which have big fish and some which have big fish on occasion. Then there are lakes I've heard/dreamed about that I really want to fish, but it takes time, money, and an understanding boss, etc.

The main thing about fishing for trout in the big reservoirs in eastern Washington is timing. February through March is ideal, April is kind of the end of things if you want to fish with light gear and no downriggers. Although, I spent one opening (Banks is open all year, but the irony of the situation was not lost on me) weekend fishing on Banks while the westsiders were fishing Blue, Park and so on. We caught trout up to seven pounds with plenty of three to five pound fish.

Hmmmm... just thinking about some of those lakes makes my piscatorial mouth water.