Heat the olive oil in a large skillet over medium heat.
Add beef cubes and sauté for 5 minutes or until browned; remove from skillet and set aside. To the same skillet, add carrots, celery and onion; season with salt and pepper and sauté for 10 minutes.
Place all ingredients in a slow cooker along with remaining ingredients (broth through squash). Cover and cook on LOW for 8 hours or until beef and vegetables are fork-tender.