This study's purpose is to assess the stress distribution in the peri-implant bone, implants, and prosthetic framework using two different posterior implant angles. All-on-four maxillary prostheses fabricated from feldspathic-ceramic-veneered zirconia-reinforced lithium silicate (ZLS) and feldspathic-ceramic-veneered cobalt-chromium (CoCr) were designed with 17 or 30-degree-angled posterior implants. Posterior cantilever and frontal vertical loads were applied to all models. The distribution of maximum and minimum principal stresses (sigma max and sigma min) and von Mises stress (sigma VM) was evaluated. Under posterior cantilever load, with an increase in posterior implant angle, sigma max decreased by 4 and 7 MPa in the cortical bone when ZLS and CoCr were used as a prosthetic framework, respectively. Regardless of the framework material, 17-degree-angled posterior implants showed the highest sigma VM (541.36 MPa under posterior cantilever load; 110.79 MPa under frontal vertical load) values. Regardless of the posterior implant angle, ZLS framework showed the highest sigma VM (91.59 MPa under posterior cantilever load; 218.99 MPa under frontal vertical load) values. Increasing implant angle from 17 to 30 degrees caused a decrease in sigma max values in the cortical bone. Designs with 30-degree posterior implant angles and ZLS framework material may be preferred in All-on-four implant-supported fixed complete dentures.