While financial terms were not disclosed, the transaction provides for deliveries of Oxford’s steam coal through 2015.
"Oxford has been supplying coal to BREC since the beginning of this year following our acquisition of Phoenix Coal in September 2009,” president and chief executive officer Charles Ungurean said.
“With this extension, we are proud to add Big Rivers to Oxford's growing portfolio of long-term customers."
The company’s $US32.2 million deal with Phoenix last year included all of the seller’s surface assets.
It was one of the final transactions made by Phoenix before that company exited the coal industry entirely in May 2010 and became known as Elgin Mining.
Oxford Resource Partners, which produces coal in northern Appalachia and the Illinois Basin, controlled 91.6 million tons of proven and probable reserves as of the end of 2009.
It currently operates 17 active mines managed by eight complexes, and most of its output is sold to large electric utilities with coal-fired, base-load scrubbed power plants under long-term coal sales contracts.
Oxford filed documentation with the US Securities and Exchange Commission in March for an initial public offering.
It trades on the New York Stock Exchange under the ticker symbol OXF.