Here are some great tips from the Fawnskin Flyer on cooking meat and poultry at high altitudes:
http://www.fawnskinflyer.com/2008/01/high-altitude-cooking-tips-from-fawnskin-meat-poultry/
The creators of the Fawnskin Flyer, a blog about small-town mountain living in California, know what they are talking about. Sitting at of 6,287 feet above sea level, the tiny town of Fawnskin definitely qualifies as a high altitude locale.