We reveal the potential of step-index fibers consisting of a metaphosphate glass core and a silica claddingas ultrafast octave-spanning supercontinuum source.The hybrid waveguide was fabricated by pressureassisted melt filling and possesses a sophisticated dispersion behavior with two zero group velocity dispersion points. The fiber was pumped in the anomalous dispersion regime at 1.56 mm with a 30 fs laser at pulse energies as low as 300 pJ and generated anoctave-spanning supercontinuum from 0.7 to 2.4 mm.Numerical simulations reveal soliton fission and double dispersive wave generation as dominant broadening effect. This study highlights phosphate glasses as promising candidate for the next generation of broadband photonic devices, as they allow for instance for high rare earth doping levels and dispersion post tuning via plasmonic nanoparticle growth.