Slice turkey breast in half crosswise without cutting all the way through. Open like a book. Set aside.
In bowl, whisk together cilantro, marmalade, soy sauce, olive oil, garlic, salt and pepper.
Place turkey breast in a re–sealable plastic bag; pour marinade over turkey. Seal bag and turn to coat evenly. Allow to marinate in refrigerator for at least one hour and up to 2 days.
Arrange on a greased preheated grill over medium high heat. Grill, turning once, until golden and cooked all the way through, about 20 minutes. Transfer to cutting board. Let rest for 10 minutes before slicing. Serve immediately or serve cold.
To prepare the turkey in the oven, arrange marinated turkey on a foil–lined rimmed baking sheet and roast in a 400 F (200 C) oven until turkey is cooked through and marinade is thick and bubbling, about 25 minutes.