Heat oil in a large (4 1/2 quart)Dutch oven. Add chicken and brown about 15 to 20 minutes. Remove chicken and add onion, garlic and celery to pan; sauté on medium heat about 5 minutes.
Return chicken to the pan with vegetables.
Add tomatoes, chicken broth, wine, salt, pepper, sage, thyme and bring to a boil; simmer about 45 minutes to 1 hour.
Add squash, bring to boil and simmer 30 minutes or until squash is tender.
Stir in frozen peas (optional) and reheat for a minute or two.
note:Bone-in chicken adds a little more flavor and bones can be removed after cooking but before serving stew. As a short cut, you can use boneless, skinless breasts, or if you like dark meat, substitute chicken thighs for some or all of the chicken breasts.