In a small bowl, combine olive oil, garlic powder, smoked paprika, salt, black pepper, and lemon juice to create the marinade.
Place the chicken breasts in a large resealable plastic bag or shallow dish and pour the marinade over them. Seal the bag or cover the dish and refrigerate for at least 1 hour or up to 24 hours.
Preheat the grill to medium-high heat (about 400°F / 200°C).
Remove the chicken breasts from the marinade and discard the marinade.
Place the chicken breasts on the grill and cook for 5 to 6 minutes on each side, or until the internal temperature reaches 165°F (74°C) and the chicken is cooked through.
Remove the chicken from the grill and let it rest for 5 minutes before slicing or serving.
To make ahead, allow the grilled chicken breasts to cool completely, then store them in an airtight container in the refrigerator for up to 4 days.
Reheat gently in the microwave or serve cold in salads or sandwiches.