Source : Webster's Revised Unabridged Dictionary (1913)

Oaten \Oat"en\, a.
   1. Consisting of an oat straw or stem; as, an oaten pipe.
      --Milton.

   2. Made of oatmeal; as, oaten cakes.

Source : WordNet®

oaten
     adj : of or related to or derived from oats; "oaten bread"