Inclusion Criteria:

• Histologically or cytologically documented locally advanced or metastatic solid tumors meeting the following study drug-specific criteria:
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1
• Life expectancy greater than or equal to (≥) 12 weeks
• Measurable disease, as defined by RECIST v1.1
• Adequate hematologic and end organ function as confirmed by laboratory results within 14 days prior to the first study treatment

Inclusion criteria specific to Arm A: Atezolizumab+ Ipilimumab

• Escalation stage: NSCLC participants
• Mandatory biopsy cohort: NSCLC or melanoma atezolizumab
• Prior atezolizumab-treated cohort: participants with NSCLC or melanoma previously treated with atezolizumab

Inclusion criteria specific to Arm B: Atezolizumab+ Interferon alfa-2b

• Escalation stage: RCC or melanoma participants
• Expansion stage: RCC or melanoma participants
• Mandatory biopsy cohort: RCC or melanoma participants
• Prior immunotherapy-treated cohort: participants with RCC, NSCLC, or melanoma previously treated with programmed death-ligand 1 (PD-L1)/ Programmed death 1 (PD-1)

Inclusion Criteria Specific to Arm C (Atezolizumab plus PEG-Interferon Alafa-2a):

• Cohort 1: participants with RCC
• Cohort 2: participants who were previously treated with anti-PD-L1/PD-1 with locally advanced or metastatic solid tumor (e.g., NSCLC, RCC, or melanoma)

Inclusion Criteria Specific to Arm D (Atezolizumab plus PEG−Interferon Alfa-2a +Bevacizumab)

• Cohort 1: participants with metastatic RCC with no prior line of systemic therapy for metastatic disease
• Cohorts 2-3: disease progression during or after at least one previous systemic, anti-cancer treatment for locally advanced or metastatic solid tumors; participants with sensitizing epidermal growth factor receptor (EGFR) mutations or anaplastic lymphoma kinase (ALK) rearrangements must have failed or are intolerant to prior treatment with EGFR or ALK inhibitors; participants with melanoma with actionable BRAF mutations (e.g., V600) must have failed or are intolerant to prior treatment with BRAF inhibitors

Inclusion Criteria Specific to Arm E (Atezolizumab +Obinutuzumab)

- R/M HNSCC participants with at least one prior line of systemic therapy

Inclusion Criteria Specific to prior Anti−PD-L1/PD-1 Treated Cohorts:

• No permanent discontinuation of atezolizumab or other immunotherapies due to a treatment-related adverse event
• Recovery from all immunotherapy-related adverse events to Grade less than or equal to (≤) 1 or baseline at the time of consent

Exclusion Criteria:

General Medical Exclusions:

• Pregnant and lactating women
• Any approved anti-cancer therapy, including chemotherapy or hormonal therapy, within 3 weeks prior to initiation of study treatment, with the following exception: (1) hormone-replacement therapy or oral contraceptives; (2) tyrosine kinase inhibitors (TKIs) that have been discontinued greater than (>) 7 days prior to Cycle 1, Day 1, baseline scans must be obtained after discontinuation of prior TKIs
• Investigational therapy within 28 days prior to initiation of study treatment
• History of severe allergic, anaphylactic, or other hypersensitivity reactions to chimeric or humanized antibodies or fusion proteins
• Known hypersensitivity or allergy to Chinese hamster ovary cell products or any component of the atezolizumab formulation
• History of or active autoimmune disease
• History of idiopathic pulmonary fibrosis (including pneumonitis), drug-induced pneumonitis, organizing pneumonia, risk of pulmonary toxicity, or evidence of active pneumonitis on screening chest computed tomography (CT) scan
• Prior allogeneic bone marrow transplantation or prior solid organ transplantation
• History of human immunodeficiency virus (HIV)
• Participants with active hepatitis B
• Participants with active hepatitis C
• Participants with active tuberculosis
• Participants with a history of confirmed progressive multifocal leukoencephalopathy
• Any serious medical condition, physical examination finding, or abnormality in clinical laboratory tests that, in the investigator's judgment, precludes the participant's safe participation in and completion of the study

Cancer-Specific Exclusions:

• Active or untreated central nervous system (CNS) metastases, as determined by CT or magnetic resonance imaging (MRI) evaluation during screening and prior radiographic assessments
• 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 screening
• Leptomeningeal disease
• Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures (once monthly or more frequently); participants with indwelling catheters are allowed.
• Uncontrolled tumor-related pain
• Uncontrolled hypercalcemia or symptomatic hypercalcemia requiring continued use of bisphosphonate therapy or denosumab
• History of other malignancy within 2 years prior to screening, except for appropriately treated carcinoma in situ of the cervix, non-melanoma skin carcinoma, Stage I uterine cancer, localized prostate cancer treated with curative intent, ductal carcinoma in situ treated surgically with curative intent, or other cancers with a similar outcome

Exclusion Criteria Related to Medications:

• Prior treatment with cluster of differentiation 137 (CD137) agonists or immune checkpoint blockade therapies (Note: Participants enrolled in the prior anti−PD-L1/PD-1 treated cohorts with melanoma may have received prior anti-cytotoxic T-lymphocyte-associated protein 4 treatment or other immunotherapies)
• Treatment with systemic immunostimulatory agents within four weeks or five half-lives of the drug, whichever is shorter, prior to Cycle 1, Day 1
• Treatment with systemic immunosuppressive medications within 2 weeks prior to Cycle 1, Day 1 (the use of inhaled corticosteroids and mineralocorticoids is allowed)

Exclusion Criteria Specific to Interferon Alpha Therapy (Arms B−D):

• History of depression, suicidal ideation or behavior, bipolar disorder, or psychosis
• Hypersensitivity to interferon alpha or any component of the product

Exclusion Criteria Specific to Bevacizumab (Arm D)

• Inadequately controlled hypertension
• Prior history of hypertensive crisis or hypertensive encephalopathy
• Significant vascular disease within 6 months prior to Day 1
• History of hemoptysis
• Evidence of bleeding diathesis or significant coagulopathy (in the absence of therapeutic anticoagulation)
• History of tracheoesophageal fistula, gastrointestinal perforation, or intra-abdominal abscess within 6 months prior to Day 1
• Clinical signs or symptoms of gastrointestinal obstruction or requirement for routine parenteral hydration, parenteral nutrition, or tube feeding
• Evidence of abdominal free air that is not explained by paracentesis or recent surgical procedure
• Proteinuria, as demonstrated by urine dipstick or > 1.0 gram of protein in a 24-hour urine collection
• Metastatic disease that involves major airways or blood vessels, or centrally located mediastinal tumor masses of large volume

Exclusion Criteria Specific Obinutuzumab (Arm E)

• Hypersensitivity to obinutuzumab
• Prior treatment with obinutuzumab