Mix butter, lemon juice, paprika, oregano, garlic salt, salt, and pepper together in a bowl and pour into a resealable plastic bag. Add chicken breasts, coat with the marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator for 3 to 4 hours.

Preheat the oven to 325 degrees F (165 degrees C). Transfer chicken to a baking dish, skin-side up. Pour marinade around the chicken.

Bake, uncovered, in the preheated oven until chicken is no longer pink at the bone and the juices run clear, about 45 minutes. An instant-read thermometer inserted near the bone should read 165 degrees F (74 degrees C).