Inclusion Criteria:  ECOG performance status of 0 or 1. Histologically or cytologically confirmed, Stage IV non-squamous or squamous NSCLC. No prior treatment for Stage IV non-squamous or squamous NSCLC. Patients who have received prior neo-adjuvant, adjuvant chemotherapy, radiotherapy, or chemo-radiotherapy with curative intent for non-metastatic disease must have experienced a treatment free interval of at least 6 months from randomization since the last chemotherapy, radiotherapy, or chemo-radiotherapy cycle. Tumor TC3 or IC3, as determined by SP142 performed by a central laboratory on previously obtained archival tumor tissue or tissue obtained from a biopsy at screening. Measurable disease, as defined by RECIST v1.1. Adequate hematologic and end-organ function. Life expectancy ≥3 months. For women of childbearing potential: agreement to remain abstinent or use contraception, and agreement to refrain from donating. For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive methods, and agreement to refrain from donating sperm.  Exclusion Criteria:  Known sensitizing mutation in the EGFR gene or ALK fusion oncogene. Symptomatic, untreated, or actively progressing CNS metastases. Spinal cord compression not definitively treated with surgery and/or radiation, or previously diagnosed and treated spinal cord compression without evidence that disease has been clinically stable for ≥2 weeks prior to randomization. Current leptomeningeal disease. Uncontrolled tumor-related pain. Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures. Uncontrolled or symptomatic hypercalcemia. Malignancies other than NSCLC within 5 years prior to randomization, with the exception of those with a negligible risk of metastasis or death treated with expected curative outcome. Pregnancy or breastfeeding, or intention of becoming pregnant during study treatment or within at least 5 months after the last dose of atezolizumab and 6 months for chemotherapy. History of severe allergic, anaphylactic, or other hypersensitivity reactions to chimeric or humanized antibodies or fusion proteins. Known allergy or hypersensitivity to biopharmaceuticals produced in Chinese hamster ovary cells or any component of the atezolizumab formulation. Active or history of autoimmune disease or immune deficiency. History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis on screening chest CT scan. Positive human immunodeficiency virus (HIV) test result at screening. Patients with active hepatitis B or active hepatitis C at screening. Active tuberculosis. Severe infections within 4 weeks prior to randomization, including, but not limited to, hospitalization for complications of infection, bacteremia, or severe pneumonia. Significant cardiovascular disease.