Wash your hands well with soap and warm water for at least 20 seconds.
Wash cilantro and wrap in a paper towel to dry.
In a small bowl, mix the salsa verde, garlic, chili powder, salt, cumin and oregano.
Cut onion into slices. Place chicken and onion in the slow cooker. Pour the salsa verde mixture over the top.
Cover and cook on high for 3 hours or low for 4 hours.
Shred the chicken and toss in juice. If using cilantro, remove cilantro leaves from steams, chop and stir in. Serve in tortillas or over brown rice with your favorite toppings