In a large bowl, combine turkey breast, turkey, feta, eggs, oats, mint, onion, garlic, salt, and pepper.
Using your hands, mix gently.
On a large baking sheet, form a loaf, about 10x6x3.
Bake at 350 degrees for 40-45 minutes, or until a meat thermometer reads 165 degrees.
Meanwhile, prepare tzatziki sauce.
When meatloaf is done, remove from heat, and cool for 10 minutes.