The oscillatory convection for a real system of fluids under the joint action of buoyancy and thermocapillary effect is investigated. The nonlinear development of the oscillatory instability is studied. Two types of boundary condition are considered. In the case of periodic boundary conditions, regimes of either travelling waves or standing oscillations have been found, depending on the period of the flow. For rigid heat-insulated lateral walls, various types of symmetric and asymmetric standing waves are obtained. Transitions between the motions with different spatial structures are investigated. It is shown that in the case of rigid heat-insulated lateral walls the period of oscillations changes non-monotonically. The nonlinear oscillations exist in a finite interval of the Grashof number values, between the stability regions of a quiescent state and stationary convection.