This randomized, double-blind, placebo-controlled study will evaluate the efficacy and safety of FOLFOX/bevacizumab with onartuzumab (MetMAb) versus placebo as first-line treatment in patients with metastatic colorectal cancer.

Inclusion Criteria:

• Adult patients, >/= 18 years of age
• Histologically or cytologically confirmed adenocarcinoma of the colon or rectum in patients with metastatic (Stage IV) disease
• Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1
• Measurable disease by RECIST criteria
• Adequate organ system function, as defined by protocol

Exclusion Criteria:

• Prior systemic or radiation therapy for metastatic colorectal cancer
• Adjuvant chemotherapy (and/or chemoradiation) for colorectal cancer within 12 months prior to date of diagnosis of metastatic disease
• Previously untreated brain metastases
• History of hypersensitivity to active or inactive excipients of any component of treatment, or known dipyrimidine dehydrogenase deficiency
• Evidence of bleeding diathesis or significant coagulopathy (in the absence of therapeutic anticoagulation)
• History of hematemesis or hemoptysis \