Study of Atezolizumab in Combination With Cobimetinib in Participants With Locally Advanced or Metastatic Solid Tumors

Inclusion Criteria:

- Solid tumor that is metastatic, locally advanced or recurrent

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

- Life expectancy greater than or equal to (>/=) 12 weeks

- Measurable disease, as defined by RECIST v 1.1

- Adequate hematologic and end organ function

- Use of highly effective contraception

- Histological tumor tissue specimen

- Participants enrolling in the indication-specific expansion cohorts in Stage 2 must
consent to tumor biopsies and must have one of the following types of cancer:

- Metatastic colorectal cancer

- Non-small cell lung cancer

- Melanoma

Exclusion Criteria:

Cancer-Specific Exclusion Criteria:

- Any approved anti-cancer therapy, including chemotherapy, or hormonal therapy within 3
weeks prior to initiation of study treatment

- Treatment with any other investigational agent or participation in another clinical
trial with therapeutic intent within 28 days prior to enrollment

- Known active or untreated central nervous system (CNS) metastases

- Leptomeningeal disease

- Uncontrolled tumor-related pain or uncontrolled pleural effusion, pericardial
effusion, or ascites requiring recurrent (once monthly or more frequently) drainage
procedures

- Uncontrolled hypercalcemia or symptomatic hypercalcemia requiring continued use of
bisphosphonate therapy or denosumab

General Medical Exclusion Criteria:

- Pregnant and lactating women

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

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

- History of autoimmune disease

- Participants with prior allogeneic stem cell or solid organ transplantation

- Positive test for human immunodeficiency virus (HIV)

- Participants with active hepatitis B, hepatitis C, or tuberculosis

- Severe infections within 4 weeks prior to Cycle 1 Day 1

- Signs or symptoms of infection within 2 weeks prior to Cycle 1 Day 1

- Received therapeutic oral or IV antibiotics within 2 weeks prior to Cycle 1 Day 1

- Significant cardiovascular disease

- Major surgical procedure other than for diagnosis within 28 days prior to Cycle 1 Day
1 or anticipation of need for a major surgical procedure during the course of the
study

- Administration of a live, attenuated vaccine within 4 weeks before Cycle 1 Day 1

Exclusion Criteria Unique to Cobimetinib:

- History of prior significant toxicity from another mitogen-activated protein kinase
(MEK) pathway inhibitor requiring discontinuation of treatment

- Allergy or hypersensitivity to components of the cobimetinib formulations

- History of congenital long QT syndrome or corrected QT interval (QTc) greater than (>)
450 milliseconds at screening

- Left ventricular ejection fraction (LVEF) below institutional lower limit of normal
(LLN) or below 50%, whichever is lower, as determined by echocardiogram or Multi Gated
Acquisition Scan (MUGA) scan

- History of or evidence of retinal pathology on ophthalmologic examination that is
considered a risk factor for neurosensory retinal detachment, central serous
chorioretinopathy (CSCR), retinal vein occlusion (RVO), or neovascular macular
degeneration

- History of malabsorption syndrome or other condition that would interfere with enteral
absorption

Exclusion Criteria Related to Medications:

- Prior treatment with clusters of differentiation (CD) 137 agonists or immune
checkpoint blockade therapies, systemic immunostimulatory agents, or systemic
immunosuppressive medications