Reconfigurable Intelligent Surfaces (RIS) have emerged as a promising technology to dynamically control the wireless propagation environment, thereby enhancing network capacity and coverage. This paper presents an extensive analysis of a multi-base station RIS-assisted system with a focus on Bit Error Rate (BER) and spectral efficiency (SE). A comprehensive system model is developed and detailed derivations for the effective channel formulation, pseudo-inverse based precoding, and SE estimation under QPSK modulation are provided. Three distinct RIS phase configuration strategies are considered: random phase selection, average-based phase alignment, and an optimization-based approach. In the optimization-based method, a constrained optimization algorithm (such as SQP) is applied to maximize the effective channel gain. Extensive Monte Carlo simulations are performed over a range of transmit power levels to assess the BER and the corresponding SE. The measured BER results indicate that the optimization-based phase design significantly enhances performance, with SE approaching the theoretical maximum of 2 bits/s/Hz in high SNR conditions.