Transfer tenderloins to a cutting board and cut each one into thin pieces. Sprinkle each piece and with salt and pepper. Heat oil in skillet over medium heat; add tenderloin pieces and cook each side 3 to 5 minutes, or until they are brown and cooked thoroughly. Transfer meat to a tray and keep warm while making sauce. For sauce, heat oil in same pan; add onions and sauté until tender. Add thyme, pepper, Marzetti Light Berry Balsamic Dressing and chicken stock, Bring all to a boil. Reduce heat and simmer for 3 minutes. Add berries and continue to cook an additional 2 to 3 minutes, just until berries are tender. Serve cooked turkey slices with sauce.