Li-7 magic angle spinning nuclear magnetic resonance was used to observe coexisting cubic and tetragonal phases in Li1+xMn2O4. Cubic phase peaks are observed at 500-580 ppm vs. 1 M LiCl(aq); tetragonal phase peaks are observed around 100 ppm. Cycling Li1+xMn2O4 on the 3 V plateau does not result in significant changes in the cubic phase. A small amount of residual tetragonal phase accounting for similar to 3% of the Li-7 NMR intensity, however, is observed in spinel deep discharged to x = 1 then returned to x = 0.