Add the cream cheese, mozzarella, Parmesan, spinach, chopped artichoke hearts, garlic and red pepper flakes to a large bowl. Stir to combine. Add salt and pepper to taste.
Divide the beef into 16 equally sized balls and flatten into thin patties. Place 2 tablespoons of the cheese mixture into the middle of 8 of the patties. Add another patty on top and pinch the seams to seal.
Season the burgers with salt and pepper on both sides. Fire up your grill for medium-high direct cooking.
Lightly brush the patties on both sides with vegetable oil and add to the grill. Cook 4-5 minutes per side or until they reach the desired doneness.
Lightly toast the buns and and top with the cooked burgers.