<p>This paper scrutinizes the effect of stiffeners (configuration(s), height) on the frequency response of a moderately thick orthotropic rectangular plate with elastically restrained edges (rotational and translational springs) subjected to a point load. The Mindlin plate theory is applied to the plate, and the Timoshenko beam theory is used for the stiffeners. A semi-analytical approach based on the mode superposition method is developed to predict the forced vibration response of orthotropic rectangular stiffened plates. The free vibration analysis is carried out using dynamic Timoshenko beam mode shape trial functions within the Rayleigh–Ritz method. Several numerical examples validate the accuracy of the proposed method. Furthermore, the effect of different stiffener configurations (two transverse parallel, two longitudinal parallel, and one set of orthogonal stiffeners) and an increase in height on the rectangular orthotropic plate is shown in terms of natural frequencies, mode shapes, and forced response (resonant frequencies). Moreover, for an orthotropic plate with orthogonal stiffeners, a shift in nodal pattern has been observed for both the fundamental frequency and higher frequencies, with an increase in stiffener height. However, this effect is also explained through eigenvectors, and its influence is highlighted through frequency response.</p>