Hybrid processes have been established for the joining of thick plates. The presented approach enables single side welding of thick metal plates by combining a laser beam and two gas metal arc (GMA) welding torches in one setup. By using this hybrid process for joining high material thicknesses, manufacturing time can be significantly reduced in comparison to conventional multilayer arc welding processes. Additionally, new joint designs can be used to reduce filler metal consumption. In order to benefit from these economic advantages, and to make use of brilliant high power lasers in pipeline manufacturing, this hybrid process needs to run robustly for common gap and tolerance ranges. The process time, compared to conventional methods, will be significantly decreased, due to the use of disk lasers with a maximum output power of 16 kW combined with two high power GMA subprocesses. For process development, American Petroleum Institute (API) 5L X70 pipeline steel plates with a thickness of 23 mm have already been joined in a flat position using a single weld pass. Based on these parameter studies, the process limitations have been determined with regard to energy input, gap bridgeability, vertical edge offset, and a lateral offset of the energy sources from the weld joint. The robustness of the hybrid process developed has been demonstrated in experiments representative of the pipeline application.