Bevacizumab and Atezolizumab With or Without Cobimetinib in Treating Patients With Untreated Melanoma Brain Metastases

Inclusion Criteria: * Signed informed consent form (ICF) * Age \>/= 18 years * Ability and willingness to comply with the requirements of the study protocol * Life expectancy \> 12 weeks * Asymptomatic off steroids for at least 10 days except patients: a) who have mild symptoms from intracranial disease that do not affect their performance status; or b) who are asymptomatic, but require steroids for control of symptoms on a maximum dose of dexamethasone 4mg/day orally (PO) or equivalent * Prior therapies for extracranial metastatic melanoma including chemotherapy, BRAFi/MEKi, cytokine or vaccine therapy as long as it did not include PD-1/PD-L1. Note: Patients who are PD-1 refractory are allowed to enroll into the TACo arm if BRAFV600 wild-type is confirmed. Patients that are known to have BRAFV600 mutation must have received prior BRAFi/MEKi prior to enrolling on TACo. Patients that have received prior BRAF/MEKi have to have received their last dose of BRAF/MEKi \> 3 months prior to being treated on this study. * At least one measurable intracranial target lesion for which all of the following criteria are met: a) Previously untreated or progressive after previous local therapy b) Immediate local therapy clinically not indicated or patient is not a suitable candidate to receive immediate local therapy c) Largest diameter of \>= 0.5 cm, but =\< 3 cm as determined by contrast-enhanced MRI * Representative formalin-fixed paraffin-embedded (FFPE) tumor specimens in paraffin bloc…