The excitation of electron plasma waves by interaction of two opposed electromagnetic waves in a magnetized plasma is examined. A beat frequency wave may be resonantly generated as either of two natural modes which have frequencies small compared to the sum frequency of the source waves. An analysis is based on Maxwell's equations and the electron-gas moment equations with the pressure tensor neglected. A formula is derived for the power absorbed per unit volume of plasma in a uniform, static magnetic field. The effects of the magnitude and direction of the magnetic field on the plasma heating rate are studied numerically.