Glioblastoma multiforme (GBM) is the most frequent malignant brain tumor and it remains a lethal disease. Approximately 4 weeks post surgery for tumor resection, patients will proceed to standard of care treatment which currently consists of temozolomide (TMZ) with concurrent radiation therapy (RT) for 6 weeks. This study will add bevacizumab (BEV) to the standard of care regimen in newly diagnosed patients. The Bevacizumab will be added 2 weeks post start of RT/TMZ. Administration of bevacizumab will continue concurrently with TMZ every 2 weeks for 12 months. Blood samples will be obtained from these patients at 3 different time points during this study.