Epitaxial graphene films have been formed on the Si-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. High-k gate stack on epitaxial graphene is realized by inserting a fully oxidized nanometer thin aluminum film as a seeding layer followed by an atomic-layer deposition process. The electrical properties of epitaxial graphene films are sustained after gate stack formation without significant degradation. At low temperatures, the missing quantum-Hall effect in Hall resistance is observed along with the pronounced Shubnikov-de Hass oscillations in magneto-resistance in gated epitaxial graphene on SiC (0001).