Season the chicken with salt and pepper. Heat the olive oil in a large stockpot. Season chicken with salt and pepper and brown in small batches, being careful not to overcrowd pan. Transfer browned chicken to a deep bowl or dish.
Add onion, carrots, celery, and garlic and saute over medium-high heat, until lightly golden, 2 to 3 minutes. Add the chicken back to the pot, along with the parsley and bay leaf. Pour in 6 cups of cold water and bring to a boil. Reduce to a simmer and cook for one hour.
Skim fat from surface of stock. Using tongs or a large slotted spoon, remove chicken from the pot and set aside. Pour stock through a fine strainer, and discard vegetables and herbs. Let chicken cool, then remove meat from bones to use for soup or chicken salad if using stock for a later use; store chicken in a covered container in the refrigerator for up to 2 days. Divide stock in to smaller containers and let cool completely before covering and storing in refrigerator or freezer.