A Study Evaluating the Efficacy and Tolerability of Veliparib in Combination With Paclitaxel/Carboplatin-Based Chemoradiotherapy Followed by Veliparib and Paclitaxel/Carboplatin Consolidation in Adults With Stage III Non-Small Cell Lung Cancer (NSCLC)

1. Participants with histologically or cytologically confirmed Stage III non-small cell lung cancer (NSCLC). 2. Participants in the randomized portion of the study must have measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1 criteria. 3. Participants must have V20 (volume of lung to receive 20 Gy radiotherapy according to simulation) \< 35%. 4. Participant must have an Eastern Cooperative Oncology Group (ECOG) performance score of 0 - 1. 5. Participant must have adequate hematologic, renal, hepatic, and lung function. 6. Participant must consent to provide archived tissue or cytology sample of NSCLC lesion for analysis.

1. Participants with prior chemotherapy or radiotherapy (RT) for current NSCLC. Participants curatively treated for past early stage NSCLC greater than 3 years ago may be included. 2. Participants with prior exposure to poly-adenosine diphosphate (ADP)-ribose polymerase (PARP) inhibitors. 3. Participants with known hypersensitivity to carboplatin, paclitaxel, or formulations containing polyethoxylated castor oil (Cremophor). 4. Participants with prior mediastinal or thoracic radiotherapy. Prior tangential radiotherapy to prior breast cancer is acceptable. 5. Participants with major surgery in the 4 weeks prior to randomization (Video-assisted thoracoscopic surgery (VATS) and/or mediastinoscopy is not considered major surgery). 6. Participants with a previous or concurrent malignancy except for treated basal cell or squamous cell skin cancer, in situ cervical cancer, or other cancer for which the patient received potentially curative treatment and has been disease-free for 3 years or is considered cured by the investigator if has been disease-free for less than 3 years. 7. Participant is pregnant or lactating. 8. Participant with sensory peripheral neuropathy of ≥ Grade 2 at baseline, unable to swallow medication, or participants with prior history of seizure within the prior 12 months.