Preheat outdoor grill to HIGH.
In a large bowl, place first 8 ingredients (ground turkey through green onions); using your very clean hands, blend thoroughly then form mixture into 4 to 6 round patties.
Place turkey burgers on preheated grill then reduce grill heat to MEDIUM-HIGH. Grill patties for 5 minutes per side or until no longer pink in the centers.
To serve, layer a turkey burger, tomato slice and a portion of mashed avocado in each lettuce leaf.