For both stages, continuation of treatment beyond Cycle 1 will be at the discretion of the treating investigator. Study treatment will be discontinued in participants who experience disease progression or unacceptable toxicity, are not compliant with the study protocol, or, in their opinion or in the opinion of the investigator, are not benefiting from study treatment. However, in the absence of unacceptable toxicity, participants with second-line or greater NSCLC who are still receiving atezolizumab at the time of radiographic disease progression may be permitted to continue study treatment. Time in the study is expected to be approximately 15 months.