The Collaborative International Dictionary of English v.0.48:

Episcopate \E*pis"co*pate\, v. i. [imp. & p. p. Episcopated;
   p. pr. & vb. n. Episcopating.]
   To act as a bishop; to fill the office of a prelate. [Obs.]
   [1913 Webster]

         Feeding the flock episcopating.          --Milton.
   [1913 Webster]