The spatiotemporal evolution of steady and oscillatory convective roll patterns in a plane horizontal layer subject to steady gravity and high-frequency vibrations is investigated numerically, considering a laterally periodic convective cell with rigid, impermeable horizontal boundaries. Simulations are performed for parameters adapted to laboratory experiments with an ethanol/water mixture with negative Soret coupling between temperature and concentration fields. The characteristics of the patterns are investigated in relation to heat intensity. Bifurcation diagrams are presented in the “Rayleigh number–Gershuni number” plane.