Cook spaghetti according to package directions. Drain and set aside.
Season chicken breast tenders with salt, pepper, and greek seasoning.
In a large skillet over medium heat, heat oil, then add chicken and cook for about 5 - 7 minutes. Turn and cook for another 5 - 7 minutes. Remove from skillet.
Add another tablespoon oil and saute chopped onions for about 5 minutes. Add minced garlic and cook for about 1 minute.
Add spinach and cook down for about 3 minutes until spinach is wilted.
Place cooked pasta on a plate. Top with the spinach, garlic and onions. Top with cooked chicken.