In a small bowl, stir together onion salt, celery salt, and pepper. Rub all sides of the meat with the mixture.
In a covered grill, arrange medium-hot coals around a drip pan. Test for medium heat above the pan.**
Place seasoned ribs, meaty side up, on grill rack over drip pan, but not over coals. Insert a meat thermometer so that the bulb doesn't rest in fat or on bone. Lower the grill hood.
Grill for 1-1/4 to 1-1/2 hours or until meat thermometer registers 170 degree F (well done). Don't turn the meat during cooking. Makes 12 to 15 servings.
To test for medium heat, you should be able to hold your hand over the drip pan at food height for 4 seconds before having to pull away.
For Texas pork ribs, ask your butcher for a center-cut, bone-in loin, cut in half through the eye, with the bone on both sides.