We aimed to investigate the feasibility of delivering stereotactic radiosurgery (SRS) or hypofractionated stereotactic radiotherapy with the hybrid MRI-LINAC (MRL) system for patients with single brain metastases, and to characterize the dosimetric impact at tissue-air interfaces resulting from the electron return effect (ERE). Material/Methods: 24 patients treated for intact single brain metastases were selected for analysis. Three optimized radiotherapy plans with the same prescribed dose were generated for each case: 1) standard noncoplanar volumetric modulated arc therapy (VMAT), 2) coplanar step-and-shoot intensity modulated radiotherapy (IMRT) on the MRL in the absence (MRL_B=0), and 3) in the presence of the transverse magnetic field (MRL_B=1.5). The plans were evaluated using cumulative dose-volume histograms (DVHs) and by calculation of Paddick conformity index (PCI), V100%, V12Gy minus gross tumor volume (V12Gy – GTV), and V2Gy. The dosimetric impact of ERE to the skin and air cavities was quantified using a 5 mm rim of tissue around tissue-air boundaries. Results: All plans met the objectives with respective to target coverage and OAR constraints. Differences between all investigated dosimetric parameters significantly favored the VMAT plans as compared to the MRL_B=0 and MRL_B=1.5 plans, except for V2Gy. The VMAT plans showed a higher mean (±standard deviation) PCI compared to the MRL_B=0 and MRL_B=1.5 plans (0.85±0.08 vs. 0.79±0.09 vs. 0.78±0.11). In the presence of the magnetic field, ERE resulted in a statistically significant but small increase in mean dose and D2cc in the skin (0.08 Gy, p < 0.0001 and 0.66 Gy, p < 0.0001, respectively) and around air cavities (0.07 Gy, p = 0.0092 and 0.25 Gy, p = 0.0004, respectively). Conclusions: Stereotactic radiation to single brain metastases is feasible using the MRL Monaco treatment planning system; however, in its current iteration, application to small targets deserve careful consideration given the technical limitations resulting in less favorable plan quality compared to that of a noncoplanar standard VMAT technique. The dosimetric impact of ERE at tissue-air boundaries is minor and does not compromise target conformity or dose gradient.