Sorry I'm late...
In no particular order, I like Windsor / London ESB / S-33 / M15 which are all nearly genetically identical. They will attenuate low in the 65-ish percent range so be cognizant of that, as they cannot ferment the complex maltotriose sugar at all, however the final result is NOT overly thick or sweet or cloying, not at all. In fact I won medals with my last two examples, a silver and a gold.
In any case, don't overthink it. Oatmeal stout is a malt-dominated style. Yeast just really doesn't matter much here. That's why I use the cheap 'n' easy dried yeasts for it. But any yeast is going to give you very good results, I can nearly guarantee.