The present work focuses on the study of the thermal stability of La 62Al 14(Cu 5/6Ag 1/6) 14Ni 5Co 5 (at.%) bulk metallic glass (BMG) using the state-of-the-art high temperature in situ hard X-ray scattering techniques available at the undulator beamline ID11 of ESRF (Grenoble, France). Constant-rate heating experiments using a fast X-ray camera (time resolution of 3 s) reveal detailed information about the thermal stability of the La-based BMG. Analyzing diffraction patterns in a reciprocal space yields thermal expansion of amorphous alloy providing insight about the thermally activated relaxation effects and glass transition. We found that in the region 20 K below the glass transition ( T g = 420 K) thermal expansion curve exhibits negative slope which indicates annealing-out of the quenched-in free volumes. The glass transition appears as a brake in the value of coefficient of the volume thermal expansion α th. Furthermore, real space analysis based on reduced pair distribution function G( r) allows to trace the changes in the local atomic structure of amorphous material during constant-rate heating.