We study a situation where firms compete for quantity and lobby to reduce their costs in an oligopoly market. We consider the case where each firm’s reduced cost from a successful lobby is public information and the case where the reduced cost from a successful lobby is each firm’s private information. Under public information, there is an equilibrium where the firms randomly choose their lobby expenditures and so a firm that could benefit from greater efficiency through a successful lobby may fail to reduce its costs. On the other hand, under private information, the firms lobby more aggressively when they enjoy greater benefit from a successful lobby and so a firm that enjoys greater benefit from a successful lobby always succeeds in lobbying. If the firm’s lobby expenditures become the benefits of others in the economy, social welfare is higher under private information than under public information equilibrium. But, if the firms’ lobby expenditures vanish in the economy, the social welfare under public and private information is not obviously determined.