I need some help Super Mario RPG Question boss location

Hey Guys I have just recently gone back to my original save and have completed most of the challenges in content mode including finally beating Xion thankfully and now I am stumped trying to located the big red flying creature that frog is telling me about, The hint he keeps giving me is super veg and not very helpful there are a lot of wide open spaces lol.

There's a lot of places you can find them.  They have a 20% chance to replace the hidden monster in most areas in any given encounter.