This study is investigating how effective **olaparib**, a drug that may stop cancer cell growth, is when given for one or two years to treat advanced ovarian cancer. **Bevacizumab**, another drug, might also be used to help stop blood supply to tumors. The study involves two groups: one takes olaparib for up to two years, with or without bevacizumab for a year, and the other group takes olaparib for one year, possibly with bevacizumab. Participants will have regular blood tests and scans like CT or MRI to check their health. **Key Points**: - The study lasts up to two years with follow-ups for five years. - Participants will receive regular health check-ups and monitoring. - No prior treatment with **PARP inhibitors** like olaparib is allowed. This study is for adults with specific types of stage III or IV ovarian cancer who have completed initial chemotherapy. It requires regular visits, and participants must meet health criteria. Risks include potential side effects from the drugs being studied.