Preheat barbecue or indoor grill to medium, medium-high. Place the first 8 ingredients in a bowl and gently mix to combine. Lightly moisten your hands with cold water and divide and shape the turkey mixture into 4, 3/4" thick patties.
Lightly oil the bars of your grill. Grill the patties 4 minutes per side,
or until entirely cooked through and temperature reaches 170 degrees F in the centre of the patty. Divide and top the patties with the cheese. Cook one minute more, until the cheese is melted.
Spread the buns with mayonnaise. Top each bottom bun with a lettuce leaf. Set on the turkey burgers. Top as desired with such things as sliced tomato, onion and peppers. Set on top buns and serve.