Lorentz invariance violation (LIV) may arise from modifications to the dispersion relation of massless particles in effective models attempting to merge quantum field theories and general relativity. One way to detect or constrain LIV effects is by measuring time delays in the arrival of high-energy photons from astrophysical sources. Suitable targets are variable, distant and highly energetic objects such as pulsars, gamma-ray bursts (GRBs), and active galactic nuclei (AGN) flares. However, a major challenge arises from intrinsic time lags due to source-specific emission processes. To improve the precision of these measurements and distinguish potential LIV-induced delays from intrinsic effects, as well as improve the current exploration of LIV up to a higher energy scale, a collaborative effort has been established among major Imaging Atmospheric Cherenkov Telescopes (IACTs): H.E.S.S., MAGIC, VERITAS, and the first Large-Sized Telescope (LST-1) of CTAO. The so-called Gamma-ray LIV Working Group aims to combine observational data from multiple sources, enhancing the sensitivity and robustness of LIV searches. We present the first set of limits on the LIV energy scale derived from a combination of real data from IACTs experiments.