Mix the ingredients: In a large bowl, combine the ground turkey, spinach, feta, garlic, oregano, salt, and pepper. Mix gently with your hands or a fork until everything is evenly combined. Try not to overmix, or the burgers can turn out dense.
Form the patties: Divide the mixture into 4 equal-sized balls and press them into round patties, around ¾ inch thick. Make a shallow indent into the center of each patty with your thumb to help them cook evenly and keep them from puffing up too much. Refrigerate at least 30 minutes before cooking.
Prep the grill: Clean and oil your grill grates, then preheat to medium-high heat, around 400°F to 450°F.
Cook the burgers: Place the turkey burgers on the grill and cook for 5 to 6 minutes per side, flipping once, until the outside is lightly charred and the center reaches 165°F on an instant-read thermometer.
Rest and serve: Let the burgers rest for a few minutes, then serve on toasted buns or warm pita with tzatziki sauce, sliced cucumber, red onion, lettuce, and tomato.
Notes
Use 93% lean ground turkey for the best balance of flavor and moisture. Extra-lean turkey breast can dry out more easily.
Frozen spinach works best because it is easy to thaw, squeeze dry, and mix evenly into the burgers. Fresh spinach can be used, but it should be cooked, cooled, and squeezed dry first.
Do not skip squeezing the spinach dry. Too much moisture can make the patties soft and harder to handle.
If the burger mixture feels sticky, wet your hands lightly before shaping the patties.
For best results, avoid overmixing. Mix just until the ingredients are combined so the burgers stay tender.
Turkey burgers must be cooked to 165°F. Use an instant-read thermometer to avoid undercooking or overcooking.
No grill? Cook the burgers in a lightly oiled skillet or grill pan over medium heat for 5 to 6 minutes per side, or air fry at 375°F for 10 to 12 minutes, flipping halfway through.
Make ahead: Shape the patties up to 24 hours ahead, cover, and refrigerate until ready to cook.