An estimated 60,000 South Koreans, including 7,000 monks, gathered at City Hall in Seoul to protest against what they say is a pro-Christian bias in President Lee Myung-bak's government.
Buddhists are angry at what they see as a predominance of Christian appointees in the government and a series of recent incidents they say express an anti-Buddhist approach by the authorities.
Monks marched to Jogye Temple, home to the Jogye Order. Eight civic activists have been staying there since rallies earlier this year against Mr Lee's decision to open South Korea to US beef imports.
The protesters want Mr Lee to apologise for alleged transgressions against Buddhism, and to fire his police chief. They are particularly upset by a recent check of top monk Jigwan's car.
Mr Lee, a Presbyterian, has faced a long run of protests since his government came to power in February. Intense anger fuelled by his approval of US beef imports caused his popularity to plummet.
Religious tolerance is prized in South Korea. Buddhism is the oldest religion but officials say Christians make up about 29% of the population compared to the Buddhists' 23%.