I'm afraid Quagsire doesn't evolve, only Wooper evolves to Quagsire.
A Quagsire can't evolve into anything in any game, it's a Pokémon in it's final form.
Wooper is the Pokémon that will evolve into Quagsire and it will evolve into Quagsire starting at Level 20.
at level 20 wooper evolves in quagsire but quagsire does not evolve after it. It is the last evolution.
Quagsire does not evolve in SoulSilver. Quagsire has a previous evolution, Wooper, but not following evolution. Quagsire does not evolve in any other version, either.
Quagsire doesn't evolve. It is the final evolution of Wooper.
You can't be able to evolve Quagsire, because that is the final evolution form.
Quagsire does not evolve in Pokemon X.
A Quagsire
quagsire does not have another evolution on Pokemon diamond
Yes.
Yes, Wooper does evolve. Wooper evolves into Quagsire at level 20.
Well actually , Quagsire doesn't evolve. Quagsire's the evolved form of Wooper. Wooper evolves at lv. 20. Otherwise just use a water stone. Hope I helped!