A new digitizing and data acquisition system for the beam loss monitors is being developed for use in several accelerators of the Fermilab complex. In addition to providing diagnostic information about beam loss, the loss monitor system is designed to provide a primary protection against damage to the superconducting magnets of the Tevatron. Protecting the Tevatron magnets over the full set of collider operating conditions requires the abort logic and thresholds to be flexible and reconfigurable quickly from stored settings. A digitizer card is the core component of the system. It integrates and digitizes the current from the loss monitor chambers each beam revolution period (21 mus), maintains three running sums of up to 64k measurements, and compares the measurements and sums to programmable abort thresholds. In this paper we report on the overall system design and on tests of a prototype digitizer card during Tevatron operation.