Prepare the Turkey Mixture: In a large mixing bowl, combine the ground turkey, crumbled feta cheese, chopped basil, Greek yogurt, minced garlic, diced onion, dried oregano, and red pepper flakes. Season with salt and pepper to taste. Mix until just combined, being careful not to overwork the meat.
Form Patties: Divide the mixture into 4 equal portions and form them into patties that are about 0.75-inch thick.
Cook the Patties: In a large skillet, heat the olive oil over medium heat. Once hot, add the turkey patties. Cook for 5-6 minutes on each side, or until the internal temperature reaches 165°F (74°C) and they are golden brown. Remove from heat and let them rest for a few minutes.
Prepare the Bread: While the patties are resting, cut the ciabatta rolls in half. If desired, lightly toast them on a skillet or in a toaster for extra crunch.
Assemble the Sandwich: Start by adding a layer of baby spinach or arugula on the bottom half of each ciabatta roll. Place the turkey feta patty on top, and if you’re using them, add sliced tomatoes, cucumber, or avocado on top of the patty. Finish with the top half of the roll.
Serve: Serve immediately while the patties are warm.