Season ribs with salt, pepper, and seasoning salt, then rub the ribs with the garlic. Layer the sliced peppers and onions on top of the ribs. Wrap the ribs in foil (it is best to wrap each rib individually) and place in refrigerator to marinate fro 24-48 hours. When ready to bake, preheat oven to 250 degrees. Place ribs (still wrapped in foil) in a heavy duty pan. Place ribs on the middle rack of oven and bake for 4 hours. Make sure to check on them often. Cook ribs until they are tender, and the meat can be pulled from the bone.