(1) Background: Ultrasonography is gaining popularity as a diagnostic tool in the study of the oral mucosa. The precision of ultrasound has made it possible to identify the various layers, based on their echogenicity. The aim of this study was to perform a quantitative analysis of healthy oral mucosa based on the analysis of greyscale, echo levels (dB), and attenuation values (dB/cm). (2) Methods: Thirty-three patients (17 females and 16 males; 58.42 ± 13.29 y.o) were recruited for this study. The images were acquired with the GE Logiq-e R7 with a linear probe at 18 MHz frequency (harmonic). For each tissue (epithelium, rete ridges, connective tissue, muscle, and bone), regions of interest were traced for the analysis of echo levels, grey levels, and attenuation values. One-way ANOVA and pairwise comparison were performed. (3) Results: Three-hundred and thirty images were analyzed. Analysis of echo levels and grey levels showed a significant difference between epithelium and rete ridges (p = 0.001), and between rete ridges and connective tissue (p = 0.001), but not between epithelium and connective tissue (p = 0.831) or connective and muscle layers (p = 0.383). The attenuation values appeared to be specific for each tissue layer (p = 0.001). (4) Conclusions: Quantitative analysis applied to ultrasound imaging of the oral mucosa allows the definition of specific tissue areas.