Mark G. Beilke, a principal and director of employee benefit research at Milliman USA in Washington, was found dead Sunday in his home. His age was not immediately known. Marjorie N. Taylor, a spokeswoman for Milliman, said details about the death are not yet known. Mr. Beilke, a consulting actuary, was originally from Wisconsin, and his funeral will be held there. Further details were not available by press time.