The nonlinear analysis of a beam resting on nonlinear random tensionless soil was studied with the aim of quantifying the influence of the spatial variability of the tension soil characteristics on the behavior of the beam and illustrating the importance of the geometric nonlinear analysis of a beam. The soil-structure interaction mechanism is taken into account where the soil is modeled as nonlinear. Due to large deflections and moderate rotations of the beam, the Von-Kàrman type nonlinearity based on the finite element formulation of nonlinear beam response is adopted, and the frictional resistance at the beam’s interface is taken into account. The study assesses the impact of various factors, including geometric and material nonlinearities, as well as the spatial variability of soil properties, aiming to understand the behavior of the beam in real-world conditions. Additionally, the study seeks to determine the effectiveness of a probabilistic approach in evaluating the reliability of the beam’s response. The results indicate that the probabilistic approach of the soil and the geometric nonlinearity of the beam serve a major role in the evaluations of the beam response.