Collective light-matter interactions have been used to control chemistry and energy transfer, yet accessible approaches that combine abinitio methodology with large many-body quantum optical systems are missing due to the fast increase in computational cost for explicit simulations. We introduce an accessible abinitio quantum embedding concept for many-body quantum optical systems that allows us to treat the collective coupling of molecular many-body systems effectively in the spirit of macroscopic quantum electrodynamics while keeping the rigor of abinitio quantum chemistry for the molecular structure. Our approach fully includes the quantum fluctuations of the polaritonic field and yet remains much simpler and more intuitive than complex embedding approaches such as dynamical mean-field theory. We illustrate the underlying assumptions by comparison to the Tavis-Cummings model. The intuitive application of the quantized embedding approach and its transparent limitations offer a practical framework for the field of abinitio polaritonic chemistry to describe collective effects in realistic molecular ensembles.