This trial studies how well atezolizumab added to the usual radiation therapy works in treating patients with stage I-IIA non-small cell lung cancer. Immunotherapy with monoclonal antibodies, such as atezolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Radiation therapy, such as stereotactic body radiation therapy, uses special equipment to position a patient and deliver radiation to tumors with high precision. This method can kill tumor cells with fewer doses over a shorter period and cause less damage to normal tissue. Giving atezolizumab and radiation therapy may work better than radiation therapy alone in treating patients with early non-small cell lung cancer.