Split, butter, and grill to golden brown the heel and crown of the bread. Evenly spread mayonnaise on bread.
Heat Roasted onions and peppers on grill. About 30 seconds prior to removing the turkey burgers from the grill, top them with with heated onions and peppers, then with cheese. Cover with lid to allow heat to melt cheese.
On the crown, place tomato slices and lettuce. On the heel, place the dressed turkey burger, then top with the dressed crown.