Important information in a company is information about the company's profit. The objective study is looking for the influence of Investment opportunity set and corporate governance mechanism at consists of the audit committee, institutional ownership managerial ownership, and board of commissioners of the quality of earnings as measured by Earnings Response coefficient. This study uses a sample of 42 manufacturing companies ted in Indonesia Stock Exchange in the year 2005-2009 The results of this study indicate that the Investment opportunity Set have a significant effect on Earnings Response Coefficient. Investment opportunity Set negatively affect the Earnings Response Coefficient, so it can be said that the increase of Investment Opportunity Set may weaken Earnings Response Coefficient of a company. Unlike the Corporate governance mechanism that consists of the audit committee, institutional ownership, managerial ownership, and board of commissioner the results indicate that corporate governance mechanisms do not have a significant effect on Earnings Response Coefficient of a company.