This randomized phase II clinical trial studies the side effects and how well proton beam or intensity-modulated radiation therapy works in preserving brain function in patients with IDH mutant grade II or III glioma. Proton beam radiation therapy uses tiny charged particles to deliver radiation directly to the tumor and may cause less damage to normal tissue. Intensity-modulated or photon beam radiation therapy uses high-energy x-ray beams shaped to treat the tumor and may also cause less damage to normal tissue. Patients will be more likely to be randomized to proton beam radiation therapy. It is not yet known if proton beam radiation therapy is more effective than photon-based beam intensity-modulated radiation therapy in treating patients with glioma.