This is a Phase IIIb multicentre, randomised, blinded, triple dummy, parallel group study to evaluate the efficacy and safety of UMEC/VI inhalation powder (62.5/25 microgram [mcg] Once daily [QD]) when administered via ELLIPTA® Dry Powder Inhaler (DPI) compared to indacaterol plus tiotropium (150 mcg/18 mcg respectively QD) administered via individual inhalers over a treatment period of 12 weeks in participants with moderate to very severe Chronic Obstructive Pulmonary Disease (COPD). The purpose of this study is to demonstrate that UMEC/VI (delivered via ELLIPTA DPI), when used in symptomatic moderate to very severe COPD participants, is non-inferior to the combination of indacaterol (delivered via BREEZHALER® inhaler) plus tiotropium (delivered via HANDIHALER® inhaler) on measures of trough forced expiratory volume in one second (FEV1) after 12 weeks of treatment. Participants who met the eligibility criteria at screening (Visit 1) will complete a 5 to 7 day run in period prior to randomisation at Visit 2. Clinic visits will follow at day 2, week 2, week 4, week 8 and week 12 of treatment, plus week 12 + 1 day (Visits 3 to 8). The total duration of study participation will be approximately 14 weeks. ELLIPTA is a registered trademark of the GSK group of companies. HANDIHALER is a registered trademark of Boehringer Ingelheim Pharma GmbH & Co. KG. BREEZHALER is a registered trademark of Novartis AG.