Prepare the Chicken:
In a small bowl, mix the olive oil, garlic powder, smoked paprika, salt, and pepper. Rub the mixture evenly over the chicken thighs. Cover and let marinate for at least 30 minutes, or overnight in the refrigerator for more flavor.
Make the Bourbon Peach BBQ Sauce:
Heat olive oil in a small saucepan over medium heat. Add the chopped onion and garlic, sautéing until softened and fragrant (about 3–4 minutes). Add the peach preserves, ketchup, bourbon, apple cider vinegar, Worcestershire sauce, smoked paprika, and cayenne pepper (if using). Stir to combine. Bring the mixture to a simmer and cook for 10–12 minutes, stirring occasionally, until the sauce thickens slightly. Taste and adjust seasoning with salt and pepper.
Preheat the Grill:
Preheat your grill to medium heat (about 375°F/190°C). If using a stovetop grill pan, heat it over medium heat and lightly grease with oil.
Grill the Chicken:
Place the chicken thighs skin-side down on the grill. Cook for 6–8 minutes per side, or until the chicken is cooked through and registers an internal temperature of 165°F (74°C).
Glaze with BBQ Sauce:
During the last few minutes of cooking, generously brush the chicken with the bourbon peach BBQ sauce. Flip and repeat on the other side, allowing the sauce to caramelize slightly on the grill.
Serve and Enjoy:
Remove the chicken from the grill and let it rest for a few minutes. Serve hot with extra bourbon peach BBQ sauce on the side.