In this paper, we consider beamformer design for multi-group multicasting where a common message is transmitted to the users in each group. We propose a novel effective alternating direction method of multipliers (ADMM) formulation in order to reduce the computational complexity of the existing state-of-the-art algorithm for multi-group multicast beamforming with per-antenna power constraints. The proposed approach is advantageous for the scenarios where the dimension of the channel matrix is less than the number of antennas at the base station. This case is always valid when the number of users is less than that of antennas, which is a practical situation in massive-MIMO systems. Simulation results show that the proposed method performs the same with significantly less computational time compared to the benchmark algorithm.