Inclusion Criteria:

          -  Patient must have histologically or cytologically proven stage I-IIA or limited T3N0M0
             non-small cell lung cancer (NSCLC), without radiographic evidence of nodal or distant
             involvement (N0M0). Patient may have T3 disease with the exclusion of multifocal
             tumors and pericardial involvement

          -  Disease must have one or more of the following high-risk features:

               -  Tumor diameter >= 2 cm as assessed by diagnostic computed tomography (CT)

               -  Tumor standard uptake value (SUV) max >= 6.2 as assessed by fludeoxyglucose F-18
                  (FDG) positron emission tomography (PET)/CT

               -  Moderately differentiated, poorly differentiated, or undifferentiated histology

          -  Patient must have undergone diagnostic chest CT with contrast (unless medically
             contraindicated) within 42 days prior to randomization. PET-CT may be used if the CT
             portion is of identical diagnostic quality to a stand-alone CT. All disease must be
             assessed within 42 days prior to randomization

          -  Patient must have undergone FDG PET/CT of chest within 90 days prior to randomization

          -  Patient must not have evidence of hilar or mediastinal nodal involvement. Any patient
             with radiographically suspicious hilar or mediastinal nodes (including features such
             as non-calcified nodes with a short axis diameter > 1 cm, abnormal morphology, and/or
             elevated FDG avidity) must undergo cytologic sampling of suspicious nodes to rule out
             involvement prior to randomization. Mediastinal nodal sampling for other patients is
             optional

          -  Patient must have undergone history and physical examination within 28 days prior to
             randomization

          -  Patient must be medically or surgically inoperable as documented by a board certified
             thoracic surgeon or multi-disciplinary tumor board consensus OR patient's
             unwillingness to undergo surgical resection must be clearly documented

          -  Patient must not have received any prior treatment for the current NSCLC diagnosis

          -  Patient must not have undergone prior radiation to overlapping regions of the chest
             that, in the opinion of the treatment physician, will interfere with protocol
             treatment

          -  Patient must not have received treatment with systemic immunostimulatory or
             immunosuppressive agents, including corticosteroids, within 14 days prior to
             randomization

          -  Patient must be >= 18 years old

          -  Patient must have Zubrod performance status of 0-2

          -  Patient must have adequate liver function defined as aspartate aminotransferase (AST)
             and alanine aminotransferase (ALT) =< 3 x institutional upper level of normal (IULN)
             within 28 days prior to randomization

          -  Patient must have adequate renal function defined as calculated creatinine clearance
             >= 30 mL/min using the following formula. The serum creatinine value used in the
             calculation must have been collected within 28 days prior to randomization

          -  Patient must have absolute neutrophil count (ANC), platelets, and hemoglobin measured
             within 28 days prior to randomization. The purpose of these tests is to collect
             baseline values to compare with on-treatment values

          -  Patient must have thyroid-stimulating hormone (TSH) measured within 28 days prior to
             randomization. The purpose of this test is to collect baseline values to compare with
             on-treatment values

          -  Patient must not have significant cardiovascular disease (New York Heart Association
             [NYHA] class II or greater)

          -  Patient must not have myocardial infarction within 90 days prior to randomization

          -  Patient must not have unstable arrhythmias or unstable angina

          -  Patient must not have known left ventricular ejection fraction < 40% within 28 days
             prior to randomization

          -  Patient must not have had an infection >= grade 3 (Common Terminology Criteria for
             Adverse Events [CTCAE] version 5.0) within 28 days prior to randomization

          -  Patient must not have an active autoimmune disease that has required systemic
             treatment in past two years (i.e., with use of disease modifying agents,
             corticosteroids or immunosuppressive drugs). Replacement therapy (e.g., thyroxine,
             insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary
             insufficiency) is not considered a form of systemic treatment and is allowed

          -  Patient must be tested for hepatitis B within 28 days prior to randomization. Patient
             must not have active (chronic or acute) hepatitis B virus (HBV) infection. Patients
             may have past or resolved HBV infection. Active HBV is defined as having a positive
             hepatitis B surface antigen (HBsAg) test. Past or resolved HBV is defined as having a
             negative HBsAG test and a positive total hepatitis B core antibody (HBcAb) test

          -  Patient must be tested for hepatitis C within 28 days prior to randomization. Patient
             must not have active hepatitis C virus (HCV) infection. Active HCV is defined as
             having a positive HCV antibody test followed by a positive HCV RNA test

          -  Patient must have an forced expiratory volume in 1 second (FEV1) >= 700 cc and a
             diffusion capacity of the lung for carbon monoxide (DLCO) >= 5.5 m/min/mmHg from
             pulmonary function testing documented within 90 days prior to randomization

          -  Patient must not have known human immunodeficiency virus (HIV) unless he/she is on
             effective anti-retroviral therapy, has had at least one viral load test within 6
             months prior to randomization, and had undetectable viral load at all viral load tests
             within 6 months prior to randomization

          -  Patient must not have a history of clinically significant interstitial lung disease or
             evidence of active pneumonitis on the screening chest CT

          -  Patients must not have a prior or concurrent malignancy whose natural history or
             treatment has the potential (in the opinion of the treating physician) to interfere
             with the safety or efficacy assessment of the investigational regimen

          -  Patients must not be pregnant due to the potential teratogenic side effects of the
             protocol treatment. Women of reproductive potential and men must have agreed to use an
             effective contraception method for the duration of protocol treatment, and for 5
             months (150 days) after the last dose of atezolizumab. A woman is considered to be of
             "reproductive potential" if she has had a menses at any time in the preceding 12
             consecutive months. In addition to routine contraceptive methods, "effective
             contraception" also includes heterosexual celibacy and surgery intended to prevent
             pregnancy (or with a side-effect of pregnancy prevention) defined as a hysterectomy,
             bilateral oophorectomy or bilateral tubal ligation. However, if at any point a
             previously celibate patient chooses to become heterosexually active during the time
             period for use of contraceptive measures outlined in the protocol, he/she is
             responsible for beginning contraceptive measures. Because there is an unknown but
             potential risk for adverse events in nursing infants secondary to treatment of the
             mother with atezolizumab, breastfeeding must be discontinued prior to randomization

          -  Patient must agree to have specimens submitted for translational medicine and banking

          -  Patients must be informed of the investigational nature of this study and must sign
             and give written informed consent in accordance with institutional and federal
             guidelines

          -  As a part of the OPEN registration process the treating institution's identity is
             provided in order to ensure that the current (within 365 days) date of institutional
             review board approval for this study has been entered in the system

          -  Patients who can complete quality of life instruments in English, French, or Spanish
             must agree to complete the questionnaires at the protocol-specified time points