Key Inclusion Criteria:

          -  Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1

          -  Histologically or cytologically confirmed diagnosis of squamous cell carcinoma of the
             esophagus

          -  Unresectable disease ineligible for curative surgery based on the documented opinion
             of the qualified medical, surgical or radiation oncologist and is not expected to
             undergo tumor resection during the course of the study

          -  Definitive concurrent chemoradiation treatment according to regional oncology
             guidelines for esophageal cancer

          -  Representative archival formalin-fixed, paraffin-embedded (FFPE) tumor specimens,
             collected prior to initiation of definitive concurrent chemoradiotherapy

          -  Adequate hematologic and end-organ function

          -  Women of childbearing potential must remain abstinent or use contraceptive methods
             with a failure rate of < 1% per year during the treatment period, for 5 months after
             the final dose of atezolizumab/placebo, and for 90 days after the final dose of
             tiragolumab/placebo, whichever is later

          -  Men must agree to remain abstinent (refrain from heterosexual intercourse) or use a
             condom, and agree to refrain from donating sperm during the treatment period and for
             90 days after the final dose of tiragolumab/placebo.

        Key Exclusion Criteria:

          -  Prior treatment with CD137 agonists or immune checkpoint blockade therapies, including
             anti-CTLA-4, anti-PD-1, anti-PD-L1 and anti-TIGIT therapeutic antibodies

          -  Any unresolved toxicity of National Cancer Institute's (NCI) Common Terminology
             Criteria for Adverse Events (CTCAE) Grade ≥ 2 from the prior chemoradiation therapy
             with the exception of irreversible and manageable hearing loss

          -  Prior allogeneic stem cell or solid organ transplantation

          -  Active or history of autoimmune disease or immune deficiency

          -  History of idiopathic pulmonary fibrosis, organizing pneumonia (e.g., bronchiolitis
             obliterans), drug-induced pneumonitis, or idiopathic pneumonitis, or evidence of
             active pneumonitis

          -  Malignancies other than esophageal cancer within 2 years prior to screening, with the
             exception of malignancies with a negligible risk of metastasis or death

          -  Treatment with any other investigational agent, including epidermal growth factor
             receptor (EGFR) inhibitors, with therapeutic intent for esophageal cancer prior to
             randomization.