Inclusion Criteria:

          -  Histologically or cytologically documented, locally advanced or metastatic NSCLC.

          -  Participants in Stage 1 (Safety Evaluation) receiving erlotinib: No limit to the
             number of prior therapies (except for EGFR TKIs).

          -  Participants in Stage 2 (Expansion) receiving erlotinib: i) sensitizing mutation in
             the EGFR gene and ii) consent to collection of tumor tissue samples before, during,
             and after treatment for biopsy and PD biomarker analyses.

          -  Participants receiving alectinib in either Stage 1 or Stage 2: must be ALK positive as
             assessed by Food and Drug Administration (FDA) approved test and must not have
             received prior treatment for their advanced NSCLC.

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

          -  Life expectancy of at least 12 weeks.

          -  Measurable disease, as defined by RECIST Version 1.1 (v1.1).

          -  Adequate hematologic and end-organ function.

          -  Use of highly effective contraception (as defined by protocol) and until 5 months
             after the last dose of atezolizumab and for 3 months after the last dose of alectinib
             or for 2 weeks after the last dose of erlotinib, whichever is longer; Males must also
             refrain from sperm donatation during this same time period. Participants must not be
             pregnant or breastfeeding.

          -  Archival tumor tissue specimen meeting protocol specifications or the participant will
             be offered the option of a pre-treatment biopsy to obtain adequate tissue sample.

        Exclusion Criteria:

          -  For participants receiving erlotinib group: prior treatment with any EGFR
             mutant-targeting TKI

          -  Any approved anticancer therapy, including chemotherapy, or hormonal therapy (except
             hormone-replacement therapy or oral contraceptives) within 3 weeks of first dose.

          -  Treatment with any other test drug or participation in another clinical trial within
             28 days of enrollment.

          -  Known symptomatic central nervous system (CNS) metastases. Participants with a history
             of treated or untreated asymptomatic CNS metastases may be eligible.

          -  Leptomeningeal disease.

          -  Uncontrolled tumor-related pain.

          -  Uncontrolled pleural effusion, pericardial effusion, or ascites requiring drainage at
             least once monthly.

          -  High levels of calcium requiring bisphosphonate therapy or denosumab.

          -  Malignancies other than NSCLC within 5 years prior to enrollment, with the exception
             of those with a negligible risk of metastasis or death (such as adequately treated
             carcinoma in-situ of the cervix, basal or squamous cell skin cancer, localized
             prostate cancer, or ductal carcinoma in situ).

          -  History of severe allergic, anaphylactic, or other reactions to chimeric or humanized
             antibodies or fusion proteins.

          -  Known hypersensitivity to biopharmaceuticals produced in Chinese hamster ovary cells
             or any component of the atezolizumab formulation.

          -  History of autoimmune disease.

          -  Participants with prior bone marrow or solid organ transplantation.

          -  History of lung inflammation or disease.

          -  Serum albumin less than (<) 2.5 grams per deciliter (g/dL).

          -  Positive for Human Immunodeficiency Virus (HIV).

          -  Liver disease.

          -  Current or active tuberculosis, hepatitis B, or hepatitis C.

          -  Participants with past or resolved hepatitis B virus (HBV) infection are eligible;
             participants positive for hepatitis C virus (HCV) antibody are eligible only if
             polymerase chain reaction (PCR) is negative for HCV Riboxy Nucleic Acid (RNA).

          -  Signs or symptoms of infection within 2 weeks prior to first dosing.

          -  Received therapeutic oral or IV antibiotics within 2 weeks prior to first dosing.

          -  Significant cardiovascular disease.

          -  Major surgical procedure other than for diagnosis within 28 days prior to first dosing
             or during the course of the study.

          -  Administration of a live, attenuated vaccine within 4 weeks before first dosing or
             during the study.

          -  Any other diseases, metabolic dysfunction, physical examination finding, or clinical
             laboratory finding that may reasonably prevent the participant from participating.

          -  Hypersensitivity to erlotinib or alectinib or to any of the excipients.

          -  Any significant ophthalmologic abnormality. The use of contact lenses is not
             recommended during the study.

          -  For participants receiving alectinib: baseline Fridericias corrected QT interval
             (QTcF) greater than (>) 470 milliseconds (ms) or symptomatic bradycardia.

          -  Prior treatment with CD137 agonists or immune checkpoint blockade therapies.

          -  Treatment with systemic immunostimulatory agents within 6 weeks or five half-lives of
             the drug, whichever is shorter, prior to first dosing.

          -  Treatment with systemic immunosuppressive medications within 2 weeks prior to first
             dosing (inhaled corticosteroids and mineralocorticoids are allowed).

          -  Participants who received acute, low-dose systemic immunosuppressant medication or a
             one-time pulse dose of systemic immunosuppressant medication are elgible for study
             after discussion and approval by the Medical Monitor.