Gather all ingredients and measure them out before starting.
In a small bowl, mix together the dried oregano, salt, and ground black pepper.
Rub the spice mixture all over both sides of the chicken breasts, pressing to adhere.
Melt the butter in a skillet over medium heat.
Cook the seasoned chicken in the butter for 3 to 5 minutes per side until lightly browned. Do not move the chicken while it sears. Transfer the browned chicken to the slow cooker.
In the same skillet, combine the water, fresh lemon juice, minced garlic, and chicken bouillon granules. Bring to a boil, stirring to dissolve the bouillon and scraping up any browned bits from the bottom of the pan.
Pour the lemon garlic mixture over the chicken in the slow cooker.
Cover and cook on Low for 6 hours or on High for 3 hours, until the chicken reaches an internal temperature of 165°F. Do not lift the lid during cooking.
Add the chopped fresh parsley 15 to 30 minutes before the end of the cooking time.
Serve hot with rice, roasted vegetables, mashed potatoes, egg noodles, or a fresh salad.