Hey Supa,
A mixed ration is better, but you usually need about 100 head on feed to cash flow a new mixer wagon (so 50 head could cash flow a used one).
Cattle (specifically their rumen) love consistency.  Every time there is a change in the diet, that brewery on 4 legs has to adjust it's rumen population, so it takes nutrients to do that instead of growing.  The more consistent the ration is from day to day, the better the cattle will do.  This includes nutrient levels, ingredient selection, time of day they are fed, etc.
As I recall, you pretty much have to process the oats and the barley so the roller mill is good.  Don't get it too fine.  I think I'd start with the oats and then go to barley if you can - barley has more energy than oats.  Be sure to have a mineral, trace mineral, vitamin, and Rumensin source in your diet too.  A pelleted protein supplement would probably work best with 10 head.
If you plan on using baleage, than harvest shell corn and not corn silage - you don't need more roughage in the diet.