Locals also call Beijing cuisine "capital city cuisine" for the simple reason that the city was also the capital during the Liao, Jin, Yuan, Ming and Qing dynasties. The Ming excepted, the rulers of all these dynasties were from northern nomadic tribes. Thus for all the 500-plus years spanning the other four dynasties, Beijing dishes were dominated by meat - the staple of the ruling classes.

During those times, Beijing was the gathering place of the literati and officials, in whose wake came countless skilled chefs from many parts of China. Naturally they brought their differing local cuisines with them, greatly enriching such local dishes as existed. Shandong, Huaiyuang and Jiangsu-Zhejiang cuisines in particular were strong influences. Because Shandong is near Beijing, more of its people than from elsewhere migrated to the capital in search of a living, many of them entering the catering sector.

As Shandong cuisine was similar to Beijing's, the variations in its dishes were quickly accepted. For example, quick-fired mutton, a common and widely popular meal to this day, calls for the cooking skills and flavoring methods which originated in Shandong.
Those times also saw Beijing engaged in trade and cultural exchanges with other parts of China. Thus many southern Chinese gravitated to the capital, chefs among them (and as they still do today). When southern food was introduced in the north, some of its flavors were changed to suit Beijing palates. This was because southern cuisines were sweeter and less salty than in the north, where people preferred salty, rich flavors. The end result was numerous dishes that combined southern and northern characteristics.

Beijing Cuisine is notable for its hundreds of dishes with special flavors that will not be found elsewhere in China. The cuisine does not emphasize strangeness or even uniqueness, just delicious food made from common ingredients and providing very agreeable tastes.

from expatsinchina