Much of the literature on the power of elected officials and bureaucratic agencies argues, from an empirical perspective, that bureaus appears to exercise autonomy. In this paper, a theoretical model sets out the conditions under which the Congress, the President, and one agency (we use the U.S. Federal Reserve as an extended example) can dictate policy outcomes. The results of the paper include the Congressional Dominance theorem: If more than 2/3 of House members, and more than 2/3 of Senate members, agree on something, they get it. The theorem is obvious (the proof is in the U.S. Constitution), but often forgotten in the substantive literature. More realistic results are derived for situations where the preferences of members of Congress are more diverse. Powers of the President to influence policy with, and without, appointments are also analyzed.