The magnetization reversal in a series of rf-sputtered FeSiAl(N) films has been studied using magnetic force microscopy. A system has been developed which has the capability to image domain structure while an in-plane magnetic field is applied in situ. All films exhibited a stripe domain structure in zero applied field which was indicative of a perpendicular component of domain magnetization which alternates in sign. All films showed a similar sequence of magnetization processes: on reducing the applied field from saturation a fine stripe domain structure nucleated and then coarsened as the field was decreased to zero. Local switching of domain contrast was observed along the steepest part of the hysteresis loop as the perpendicular component reversed. As the reverse field was increased toward saturation, the stripe domains disintegrated into smaller regions. This observation is consistent with an interpretation that the domain magnetization rotated locally into the sample plane. The saturation field and the film stress exhibited similar trends with nitrogen partial pressure. The results suggest that the perpendicular anisotropy that caused the formation of the stripe domain structure could be induced by the film stress via magnetoelastic coupling.