Heat grill to medium heat. Spray with nonstick cooking spray.
Add pork and cook for 20-25 minutes or until fully cooked. Allow the pork to rest on a cutting board for 5 minutes before slicing.
While the pork is cooking make the sauce. Add hoisin sauce, soy sauce and oyster sauce to a large skillet or pan. Cook over low heat until heated through.
Cube the cooked pork into bite sized pieces.
Toss the cubed pork into the sauce.
Serve immediately over bib lettuce with green onions and sesame seeds, if desired.