In a large bowl, mix together the Greek yogurt, lemon juice, minced garlic, salt, pepper, oregano, and olive oil.
Add in the chicken tenderloins and make sure they are fully covered in the marinade.
Place in the fridge to marinate for at least 15 minutes. If you can even do 30 minutes or an hour, do it!
If you plan on grilling, heat up the grill.
Using tongs, place the marinated chicken on the hot grill (or a cast-iron skillet or grill pan). Cook on each side for at least 5 minutes, or until the chicken is fully cooked through. To test, remove a tender and cut it in half to see if it is no longer pink on the inside.
Serve any way you like! For an easy lunch or dinner, serve it with toated pita, fresh cut vegetables, mixed greens, and tzatziki sauce.