yeah man, i have the same experience. but as people wrote here, the QuakeMOS port exists and works fine. get it from morphos-news.de , directory game/shoot. it contains quakemos executable. put it into your quake directory, click it and there you go!!! Original installer from the CD works w/o problems under MorphOS so i presume you already have your Quake installed... have fun with it and write if u succeeded running the game...
btw: AlienBreed 3d2 works great under MOS and is much athmospherical than Quake or Doom or Duke3D
pecaN of the Czech PowerPC User Group