Red Robin Gourmet Burgers Inc. said late Wednesday that Chief Executive Denny Post will retire effective Wednesday. Red Robin said that the company has formed a search committee to find a replacement and in the interim has appointed board chair Pattye Moore temporary CEO. Red Robin stock was down less than 1% in the extended session. Red Robin shares fell 1.1% during the regular session Wednesday, as the S&P 500 index rose 0.2%.Market Pulse Stories are Rapid-fire, short news bursts on stocks and markets as they move. Visit MarketWatch.com for more information on this news.