Objectives: It is unclear whether osteopathic manipulative treatment (OMT) affects gastric myoelectric activity (GMA), an index of gastric motility. We hypothesized that OMT significantly alters power spectral density (PSD) analyses of electrogastrography (EGG) recordings, an index of GMA, compared with time control OMT. Design: GMA data were obtained from nine subjects before and after OMT and time control on separate days in a cross-over design. Fifteen-minute EGG recordings were obtained before and after each intervention and after a water challenge (WC). Percent power in the normogastric range (PPN) was estimated from PSD analyses. Absolute percent change of PPN and dominant frequency (DF) from baseline to postintervention and baseline to post-WC was computed and compared using two-way repeated-measures ANOVA. Results: OMT altered PPN versus time control (time control: 5.3% ± 1.2%; OMT: 24.5% ± 4.5%; p = 0.015). WC altered PPN compared with time control (post-time control ΔPPN: 5.3% ± 1.2%; post-drink ΔPPN: 30.3% ± 7.2%; p < 0.01). However, WC did not alter PPN with prior OMT treatment (post-OMT ΔPPN: 24.5% ± 4.5%; post-WC ΔPPN: 19.4% ± 5.6%; p = 0.47). Nevertheless, OMT reduced the rate of change for DF compared with time control (WC post-time control: 37.9% ± 7.4%; WC post-OMT: 20.0% ± 5.9%; p = 0.02). Conclusions: We conclude that (1) OMT significantly alters GMA compared with time control and that (2) OMT reduces the rate of change in the frequency response to WC within the normal frequency range of 2-4 cycles per minute, indicating a physiological effect.