Optical phased arrays (OPAs) are devices that use the coherence of light to control the interference pattern in the far field, which enables them to steer a laser beam with no moving parts. As such, OPAs have potential applications in laser communications, target acquisition and tracking, metrology, and directed energy. In this Letter, we present a control architecture for an actively phase-locked OPA, capable of steering a laser beam at speeds limited by the actuation bandwidth of electro-optic modulators. The system achieved an output phase stability of λ/770 and steering speeds up to 1 MHz. The digital control architecture can be extended to GHz steering speeds, is readily scalable to hundreds of emitters, and is compatible with high-power arrays.