A shake table investigation was carried out on a full-scale U-shaped masonry assemblage to study the effectiveness of Steel Reinforced Grout (SRG) for the improvement of the out-of-plane seismic capacity of masonry walls. Natural accelerograms were applied with increasing scale factor up to failure. A first session of tests was performed on the unreinforced specimen, that collapsed by out-of-plane overturning. Steel tie bars were then installed to prevent overturning. In this case, severe damage developed due to bending. Finally, the wall was retrofitted with horizontal strips of Ultra High Tensile Strength Steel cords, externally bonded to the masonry with lime based mortar, and steel connectors. SRG led to a significant improvement of the seismic capacity, strongly limited damage development, and entailed small modifications of the dynamic properties of the specimen. Since the reinforcement had a thickness of less than 10mm, it is suitable for applications within the plaster layer during the maintenance work of the façades without modifying their appearance.