Study of Cobimetinib in Combination With Atezolizumab and Bevacizumab in Participants With Gastrointestinal and Other Tumors

Inclusion Criteria: * Eastern Cooperative Oncology Group performance status of 0 or 1 * Histologically confirmed unresectable metastatic colorectal adenocarcinoma * Life expectancy at least 12 weeks * Progression on a prior line of therapy that contained a fluoropyrimidine and oxaliplatin or irinotecan for unresectable metastatic colorectal adenocarcinoma * Measurable disease per RECIST v1.1 * Adequate hematologic and end organ function * Creatinine clearance greater than or equal to (\>=) 30 milliliters per minute (mL/min) * For biopsy cohort, participants must be bevacizumab naive or received the last bevacizumab treatment at least 12 months prior to Cycle 1 Day 1 and according to the investigator's judgment the planned biopsies would not expose participants to substantially increased risk of complications * For women of childbearing potential, agreement to remain abstinent (refrain from heterosexual intercourse) or use of contraceptive methods that result in a failure rate of less than (\<) 1 percent (%) per year during the treatment period and for at least 180 days after the last study treatment * For men, agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures, and agreement to refrain from donating sperm Exclusion Criteria: * More than one prior line of systemic therapy for advanced CRC * Participants with known microsatellite (MSI)-high status * Major surgery or significant traumatic injury within 60 days prior to enrollment * Minor surgical procedure within 15 days of study Cycle 1 Day 1 * Untreated central nervous system (CNS) metastases * Treatment with any investigational agent or approved therapy within 28 days * Malignancies other than colorectal cancer within 5 years prior to Cycle 1 Day 1 * Prior radiation therapy within 30 days prior to study Cycle 1 Day 1 and/or persistence of radiation-related adverse effects * Prior allogeneic bone marrow transplantation or solid organ transplant for another malignancy in the past * Spinal cord compression not definitively treated with surgery and/or radiation * Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures * Current or recent use of therapeutic oral or parenteral anticoagulants or thrombolytic agents * Intake of St. John's wort or hyperforin (potent cytochrome P450 \[CYP\] 3A4 enzyme inducer) or grapefruit juice (potent CYP3A4 enzyme inhibitor) within 7 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 biopharmaceuticals produced in Chinese hamster ovary cells or any components of cobimetinib, atezolizumab, or bevacizumab formulations * Prior treatment with clusters of differentiation (CD) 137 (CD137) agonists or immune checkpoint blockage therapies, anti-programmed death protein-1, anti-program death-ligand 1, mitogen-activated protein kinase (MEK) inhibitor * Proteinuria value \> 1.0 g at screening * Uncontrolled glaucoma with intraocular pressure ≥ 21 mmHg * Hyperglycemia (fasting) ≥ Grade 2 * Human Immunodeficiency Virus (HIV) infection * Active hepatitis B or hepatitis C * History of autoimmune disease, clinically significant cardiac or pulmonary dysfunction * Administration of a live, attenuated vaccine within 4 weeks prior to Cycle 1 Day 1 or at any time during the study and for at least 5 months after the last dose of study drug * History of or evidence of retinal pathology on ophthalmologic examination that is considered a risk factor for neurosensory retinal detachment/central serous chorioretinopathy, retinal vein occlusion, or neovascular macular degeneration * History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, or idiopathic pneumonitis * Uncontrolled tumor pain