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