A Study to Assess the Safety and Tolerability of Atezolizumab in Combination With Other Immune-Modulating Therapies in Participants With Locally Advanced or Metastatic Solid Tumors

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

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 non-squamous 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