By the time you come to use your compost then any poison in the rhubarb leaves will have long been broken down by the decomposition process. There is a lot of nonsense talked about what you can and cannot add to compost heaps. I suppose if you made compost from just rhubarb leaves and orange peel and one or two other things one is not supposed to add then your compost might not be perfect.

only poisonous if you eat the leaves. I also add them to the compost heap with no problems. their breakdown by bacteria also breaks down the toxins.

Ahh yes, that makes total sence when you think about it. Thought i was going to have to start all over again, lol silly me. Many thanks Owdboggy and Seaburngirl. :D
Ps this site is rather good, so glad i found it.

I have always add mine. As long as you have plenty of variety it will be okay.