Make slits in the roast and insert garlic slices. Combine in a large plastic bag: wine, lemon juice, olive oil, onions, bay leaves, thyme, salt and pepper. Add roast and marinate overnight in refrigerator.
Preheat oven to 350 degrees F (175 degrees C). Remove meat from marinade and roast until meat is no longer pink inside and a thermometer reads 145 degrees F (63 degrees C).