I must keep missing this episode each time it comes up in the rotation, because I never learn what causes George to leave the Yankees. Steinbrenner's incompetence and George's willingness to exploit that incompetence seem to be a perfect fit.
How did George lose his job with the Yankees?
He was "traded" to Tyler Chicken in The Muffin Tops. :-)
George meets a beautiful NYC tourism bureau employee (played by the "breathtaking" Rena Sofer), and claims he's a tourist from Arkansas in order to spend time with her. He then recreates his life in the city, telling her he found an apartment (the one he'd actually been living in) and a job (his real job with the Yankees). When she visits him at work, she congratulates Steinbrenner for taking a chance on a night hen inspector (or something like that) from Tyler Chicken.
Steinbrenner misunderstands and thinks George is moonlighting in Arkansas, so he contacts Tyler Chicken to work out an exclusive contract. In the negotiations, George is traded to Tyler Chicken in return for chicken products for the Yankee Stadium vendors.
Mike's site is down temporarily, but I believe the script from this episode is there: http://www.geocities.com/tnguym/