Inclusion Criteria: - Histologically or cytologically confirmed previously treated metastatic colorectal cancer with adenocarcinoma histology and in Stage IV per American Joint Committee on Cancer (version 4.0) at study entry - Microsatellite status should be performed per local standard of practice, immunohistochemistry (IHC) and/or PCR. If IHC results are equivocal, PCR is required for determining microsatellite stable (MSS) status - Must have measurable disease per RECIST 1.1. Participants with lesions in a previously irradiated field as the sole site of measurable disease will be permitted to enroll provided the lesion(s) have demonstrated clear progression and can be measured accurately - Eastern Cooperative Oncology Group (ECOG) Performance Status of 0-1 at screening and on cycle 1 day 1 (C1D1) Exclusion Criteria: - BRAF V600 mutant colorectal cancer - Active brain metastases or leptomeningeal metastases - Active, known or suspected autoimmune disease - Participants with a condition requiring systemic treatment with either corticosteroids (> 10 mg daily prednisone equivalents) or other immunosuppressive medications within 14 days of study treatment administration - History of interstitial lung disease or pneumonitis - Prior treatment with immune checkpoint inhibitors and mitogen-activated protein kinase enzymes (MEK) inhibitors - History of allergy or hypersensitivity to study drug components Other protocol defined inclusion/exclusion criteria apply