Here is a list of German Adjectives Starting with O.
List of German Adjectives Starting with O
Oberflächlich (superficial)
Obskur (obscure)
Objektiv (objective)
Obszön (obscene)
Offen (open)
Öffentlich (public)
Offensichtlich (obvious)
Ohrfeigenverdächtig (deserving of a slap)
Ohnmächtig (unconscious)
Ominös (ominous)
Omnipotent (omnipotent)
Onkelhaft (avuncular)
Operativ (operative)
Optimistisch (optimistic)
Opulent (opulent)
Ordentlich (orderly, tidy)
Organisch (organic)
Original (original)
Orkanartig (hurricane-like)
Orthodox (orthodox)
Ortschaftlich (local)
Ozeanisch (oceanic)