Combine the onion, garlic, sage, wine and olive oil in a large ziplock bag and squish to mix well; add the lamb chops and marinate in the refrigerator for 8 to 12 hours.
Drain the lamb chops, reserving marinade.
Pour reserved marinade into a saucepan and bring to a boil; boil for 5 minutes.
Arrange lamb chops on a grill rack.
Brush with the cooked marinade and grill until chops are cooked through (about 10 minutes per side for well done but keep checking to make sure they are not overdone), basting occasionally with the cooked marinade.
NOTE: If sage or rosemary grown in your garden, use a few sprigs as the marinade brush for extra flavor.