The trial is open to patients who have metastatic renal cell carcinoma/urothelial (bladder) carcinoma with at least 2 measurable sites of disease. All eligible patients will be randomly assigned to immunotherapy(nivolumab/atezolizumab) versus immunotherapy (nivolumab/atezolizumab) plus radiotherapy, 10 Gy x3 (conformally or by IMRT/IGRT to maximally spare normal tissue), to one of their measurable lesions. For patients assigned to the immunotherapy plus radiotherapy arm, immunotherapy treatment starts with the first radiotherapy fraction. Nivolumab will be given every 2 weeks for patients with metastatic renal cell cancer and atezolizumab will be given every 3 weeks for patients with metastatic urothelial cancer. Patients will be re-imaged at 9 week (year 1) or 12 week (years 2-3) intervals and evaluated for response (defined as an objective response of measurable metastatic sites outside the radiation field). This response will be evaluated with CT scans in non-irradiated measurable metastatic sites per RECIST version 1.1. Patients will continue to receive their respective immunotherapies for up to three years or until disease progression or until a dose limiting toxicity is reached.