Well, this increases my puzzlement. Living in Scotland, the only Oakham beer I've tasted is their "Citra", available here from Tesco. I keep dipping into commercial beers that I haven't come across before out of interest, although I normally prefer my own. For my taste, the Oakham Citra is one of the best-tasting hop-forward commercial beers available. Apart from being over-carbonated (but pretty well all bottled beers are), I find the general balance but also the hop flavour and aroma absolutely first-rate. I'd have been happy to have brewed this myself.
I'd echo The Baron's thoughts as to what exactly is "grassy". To me, it suggests new mown lawns, or possibly the cropping of a hayfield. Both similar smells, but not the same, and both smells that I love. In fact, I suspect that I'd like a beer that had that aroma. But it is not something that I've encountered in any beer, not even close.
Anyway, I have to remain confused......