Mix together oregano, salt, and pepper in a small bowl. Rub spice mixture all over chicken breasts. Melt butter in a skillet over medium heat.

Cook chicken until lightly browned, 3 to 5 minutes per side.

Place chicken in a slow cooker.

Mix water, lemon juice, garlic, and bouillon in the same skillet; bring to a boil.

Pour mixture over chicken.

Cover and cook on Low for 6 hours or High for 3 hours. Add parsley to the slow cooker 15 to 30 minutes before the end of cook time.