Disclosed is a method of copolymerizing polyethylene glycol (PEG) into polyethylene terephthalate (PET) to achieve a polyethylene glycol-modified polyester composition that can be spun into filaments. The method includes the steps of copolymerizing polyethylene glycol into polyethylene terephthalate in the melt phase to form a copolyester composition, then polymerizing the copolyester composition in the solid phase until the copolyester is capable of achieving a melt viscosity that facilitates the spinning of filaments, and thereafter spinning filaments from the copolyester. A copolyester composition comprised of polyethylene glycol and polyethylene terephthalate is also disclosed. Fabrics made from fibers formed from the copolyester composition possess wetting, wicking, draying, flame-retardancy, static-dissipation, and soft hand properties that are superior to those of fabrics formed from conventional poylethylene terephthalate fibers of the same yarn and fabric construction.