The teleconnection between the Quasi-Biennial Oscillation (QBO) and the Arctic polar vortex is investigated using Coupled Model Intercomparison Project phase 6 (CMIP6) models. We use 14 CMIP6 models, reanalysis, three experiments with prescribed QBOs, one of which has no free polar stratospheric variability, and branched runs in which a QBO is imposed in runs previously devoid of a QBO. Each CMIP6 model underestimates the Holton-Tan effect (HTE), the weakening of the polar vortex with QBO easterlies in the lower stratosphere. To establish why, 850 Kelvin potential vorticity (PV) maps are used to study zonal asymmetries in the teleconnection. The QBO initiates the HTE by promoting equatorward (poleward) intrusion of high (low) PV over mid-latitude Asia (60°E-120°E). The presence of the PV intrusion in a model response is highly correlated with polar cap warming and the HTE. Models with stronger 10 hPa QBO amplitudes generally include the PV intrusion.