By using 960 observations to investigate the effect of the interaction of the variable of the major audit offices “the Big 4” with the joint audit variable on publication lag and the total lag period. The study concluded the significance of the impact of the composition of the members of the audit team when following the joint audit approach on reducing the two periods lag (publication lag and audit report lag) in the Egyptian stock market, which means that the effect of the joint audit on both periods depends on the composition and efficiency of the audit process team ; Hence, the more the joint audit approach is adhered to in the Egyptian environment and one of its participants is a member of the major audit firms “big 4”, the more this leads to a reduction in the publication lag of financial reports and the overall period; This finding is consistent with the trend of results from several literatures dealing with the effects of joint audit.