A Study of Atezolizumab Versus Placebo in Combination With Paclitaxel, Carboplatin, and Bevacizumab in Participants With Newly-Diagnosed Stage III or Stage IV Ovarian, Fallopian Tube, or Primary Peritoneal Cancer

Inclusion Criteria:

   - Participants receiving a histologic diagnosis of epithelial ovarian cancer (EOC),
   peritoneal primary carcinoma, or fallopian tube cancer

   - Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2

   - Life expectancy greater than (>) 12 weeks

   - For participants who receive therapeutic anticoagulation: stable anticoagulant regimen

   - Availability of a representative formalin-fixed, paraffin-embedded (FFPE) tumor
   specimen in paraffin blocks (preferred) or at least 20 unstained slides (for detailed
   tissue requirements at screening)

Exclusion Criteria:

   - Received a current diagnosis of borderline epithelial ovarian tumor (formerly tumors
   of low malignant potential)

   - Have recurrent invasive epithelial ovarian, fallopian tube, or primary peritoneal
   cancer that was treated only with surgery (example [e.g.], participants with Stage IA
   or Stage IB epithelial ovarian or fallopian tube cancers)

   - Have non-epithelial ovarian tumors (e.g., germ cell tumors, sex cord stromal tumors)

   - Received prior radiotherapy to any portion of the abdominal cavity or pelvis

   - Received prior chemotherapy for any abdominal or pelvic tumor that include neoadjuvant
   chemotherapy (NACT) for ovarian, primary peritoneal or fallopian tube cancer

   - Received any biological and/or targeted therapy (including but not limited to
   vaccines, antibodies, tyrosine kinase inhibitors) or hormonal therapy for management
   and/or treatment of epithelial ovarian or peritoneal primary cancer

   - Have synchronous primary endometrial cancer

   - Have a prior history of primary endometrial cancer, except: Stage IA cancer;
   superficial myometrial invasion, without lymphovascular invasion; grade less than (<)
   3 or poorly differentiated subtypes, and this includes papillary serous, clear cell or
   other International Federation of Gynecological Oncologists (FIGO) Grade 3 lesions

   - With the exception of non-melanoma skin cancer and other specific malignancies as
   noted above, other invasive malignancies with any evidence of other cancers present
   within the last 5 years or previous cancer treatment that contraindicates this
   protocol therapy

   - Have a known hypersensitivity or allergy to biopharmaceutical agents produced in
   Chinese hamster ovary cells or any component of the atezolizumab and/or bevacizumab
   formulations

   - Undergo major surgical procedure within 28 days prior to first bevacizumab dose, or
   anticipation of the need for a major surgical procedure during the course of the study
   except participants who receive NACT and will need interval surgery. This may include
   but is not limited to laparotomy.

   - Have prior allogeneic bone marrow transplantation or solid organ transplant

   - Have any other diseases, metabolic dysfunction, physical examination finding, or
   clinical laboratory finding giving reasonable suspicion of a disease or condition that
   contraindicates the use of an investigational drug or that may affect the
   interpretation of the results

   - Have any approved or investigational anti-cancer therapy, including chemotherapy or
   hormonal therapy, with exceptions: Hormone-replacement therapy or oral contraceptives

   - Are administered treatment with any other investigational agent or participation in
   another clinical study with anti-cancer therapeutic intent

   - Have core biopsy or other minor surgical procedures within 7 days prior to the first
   dose of bevacizumab

   - Have known sensitivity to any component of bevacizumab

   - Have known sensitivity to any component of paclitaxel

   - Current treatment with anti-viral therapy for hepatitis B virus (HBV)

   - History of leptomeningeal disease