This is a randomized, Phase II, double-blind, multicenter, placebo-controlled trial designed to preliminarily estimate the efficacy and evaluate the safety and tolerability of onartuzumab (MetMAb) + bevacizumab + paclitaxel and onartuzumab + placebo + paclitaxel versus placebo + bevacizumab + paclitaxel in participants with metastatic or locally recurrent, triple-negative breast cancer who either have not received treatment (first-line) or have progressed after one conventional cytotoxic chemotherapy regimen (second-line).

Inclusion Criteria:

• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1
• Histologically confirmed estrogen receptor (ER)-, progesterone receptor (PR)-, and human epidermal growth factor 2 (HER2)-negative (triple-negative) adenocarcinoma of the breast
• Confirmed availability of tumor tissue

Exclusion Criteria:

• Prior therapy with two or more regimens for metastatic breast cancer
• Any systemic anti-cancer therapy within 3 weeks prior to Day 1 of Cycle 1
• Major surgical procedure, open biopsy, or significant traumatic injury within 30 days prior to Day 1 of Cycle 1
• Prior therapy with a taxane for metastatic breast cancer
• Prior therapy with bevacizumab, sorafenib, sunitinib, or other putative vascular endothelial growth factor (VEGF) pathway-targeted therapy following diagnosis of breast cancer
• Prior therapy with hormones and/or trastuzumab
• Inadequate hematology, renal, or hepatic organ function

Bevacizumab Exclusion Criteria:

• Uncontrolled hypertension (systolic pressure greater than [>] 150 millimeters of mercury [mmHg] and/or diastolic pressure > 100 mmHg), with or without anti-hypertensive medication
• Evidence of bleeding diathesis or coagulopathy