In this paper we propose a unified economic dispatch and frequency control framework for power systems with an increasing amount of intermittent resources such as wind and solar. While the conventional hierarchies of power system decision and control are based on the time-scale separation principles (e.g., primary, secondary, and tertiary control), the increasing penetration of variable and uncertain resources may render the assumption of time-scale separation invalid. Therefore, the decision and control obtained from the conventional hierarchies will be suboptimal in its nature. In this paper, a model-based joint economic dispatch and frequency control scheme is proposed to improve the efficiency of generation control under the new set of assumptions. Enabled by advances in faster and cheaper sensing, communication, and computing capabilities, the proposed frequency aware economic dispatch (FAED) is readily implementable for today's power system operations. In a two-area test system simulation, we illustrate that the proposed FAED complies with the present frequency performance criteria and reduces the total generation cost.