A codeword for homosexual men, dating back to the 80s and part of the early 90s. If a man wanted to signal to other homosexuals in a restaurant, he would specifically order a turkey dinner with mashed potatoes and turkey gravy on the side. Then afterwards said homosexual would head out to the nearest secluded area, usually a wooded enviroment.
Jim just ordered the Turkey Dinner with Mashed Potatoes and Gravy on the side, he must be looking for a hookup in the woods.