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
You may not be if
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
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
