Hi

I teach options at SUNY-Binghamton and was wondering how
long an OEX index trader has after the close of trading to
inform the exchange that he wishes to exercise an option.
4:15. 4:30 later or is it a grey area?


It's not grey.  There's a specific time.

When I was last trading at the CBOE, almost nine years ago, 4:15 was the cutoff time.
But to get the definitive, current answer, write to the options clearing corporation:  options@theocc.com
They will give you the correct reply.

--
Mark D. Wolfinger
The Rookie's Guide to Options:
The Beginner's Handbook of Trading Equity Options
website:  http://www.mdwoptions.com
blog: http://blog.mdwoptions.com/options_for_rookies
Free eBook: http://www.mdwoptions.com/freebook.pdf