A Study of Tiragolumab in Combination With Atezolizumab Plus Pemetrexed and Carboplatin/Cisplatin Versus Pembrolizumab Plus Pemetrexed and Carboplatin/Cisplatin in Participants With Previously Untreated Advanced Non-Squamous Non-Small Cell Lung Cancer

Key Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1 * Histologically or cytologically documented locally advanced unresectable or metastatic non-squamous NSCLC that is not eligible for curative surgery and/or definitive chemoradiotherapy * No prior systemic treatment for metastatic non-squamous NSCLC * Known tumor programmed death-ligand 1 (PD-L1) status * Measurable disease, as defined by Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1) * Life expectancy \>= 12 weeks * Adequate hematologic and end-organ function * Negative human immunodeficiency virus (HIV) test at screening * Serology test negative for active hepatitis B virus or active hepatitis C virus at screening. Key Exclusion Criteria: * Mutations in epidermal growth factor receptor (EGFR) gene or anaplastic lymphoma kinase (ALK) fusion oncogene * Pulmonary lymphoepithelioma-like carcinoma subtype of NSCLC * Symptomatic, untreated, or actively progressing central nervous system (CNS) metastases * Active or history of autoimmune disease or immune deficiency * History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, or idiopathic pneumonitis, or evidence of active pneumonitis * History of malignancy other than NSCLC within 5 years prior to randomization, with the exception of malignancies with a negligible risk of metastasis or death * Severe infection within 4 weeks prior to initiation of study treatment or any active infection that, in the opinion of the investigator, could impact patient safety * Treatment with investigational therapy within 28 days prior to initiation of study treatment * Prior treatment with CD137 agonists or immune checkpoint blockade therapies, including anti-cytotoxic T lymphocyte-associated protein 4, anti-TIGIT, anti-PD-1, and anti-PD-L1 therapeutic antibodies * Treatment with systemic immunostimulatory agents within 4 weeks or 5 drug-elimination half-lives (whichever is longer) prior to initiation of study treatment * Treatment with systemic immunosuppressive medication within 2 weeks prior to initiation of study treatment, or anticipation of need for systemic immunosuppressive medication during study treatment * Known allergy or hypersensitivity or other contraindication to any component of the chemotherapy regimen the participant may receive during the study * Women who are pregnant, or breastfeeding * Known targetable c-ROS oncogene 1 (ROS1) or BRAFV600E genomic aberration.