We present multi-frequency VLA , multicolor CCD imaging , optical spectroscopy , and ROSAT HRI observations of the giant FR II radio galaxy NVSS 2146+82 . This galaxy , which was discovered by the NRAO VLA Sky Survey ( NVSS ) , has an angular extent of nearly 20 \arcmin from lobe to lobe . The radio structure is normal for an FR II source except for its large size and regions in the lobes with unusually flat radio spectra . Our spectroscopy indicates that the optical counterpart of the radio core is at a redshift of z = 0.145 , so the linear size of the radio structure is \sim 4 h _ { 50 } ^ { -1 } Mpc , H _ { 0 } = 50 h _ { 50 } . This object is therefore the second largest FR II known ( 3C 236 is \sim 6 h _ { 50 } ^ { -1 } Mpc ) . Optical imaging of the field surrounding the host galaxy reveals an excess number of candidate galaxy cluster members above the number typically found in the field surrounding a giant radio galaxy . WIYN HYDRA spectra of a sample of the candidate cluster members reveal that six share the same redshift as NVSS 2146+82 , indicating the presence of at least a “ rich group ” containing the FR II host galaxy . ROSAT HRI observations of NVSS 2146+82 place upper limits on the X-ray flux of 1.33 \times 10 ^ { -13 } ergs cm ^ { -2 } s ^ { -1 } for any hot IGM and 3.52 \times 10 ^ { -14 } ergs cm ^ { -2 } s ^ { -1 } for an X-ray AGN , thereby limiting any X-ray emission at the distance of the radio galaxy to that typical of a poor group or weak AGN . Several other giant radio galaxies have been found in regions with overdensities of nearby galaxies , and a separate study has shown that groups containing FR IIs are underluminous in X-rays compared to groups without radio sources . We speculate that the presence of the host galaxy in an optically rich group of galaxies that is underluminous in X-rays may be related to the giant radio galaxy phenomenon .