In a bowl, whisk together olive oil, garlic, lemon juice, lemon zest, dried oregano, dried thyme, dijon, salt, and pepper.
Place the chicken breasts in the slow cooker and pour the lemon-garlic mixture over them.
Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is cooked through and tender.
Serve the chicken garnished with fresh parsley and lemon slices, alongside rice or a light salad.
