Preheat oven to 250°.

Spread onion slices evenly over a rimmed baking dish or roasting pan that is long enough to hold the ribs.

Place ribs bone side down, on top of the onions.

Pour beer over the ribs, and then sprinkle with salt and pepper.

Cover tightly with foil and bake in the preheated oven 4 hours until tender.

To finish: Heat grill to low.

Remove ribs from the oven and transfer to grill, bone side down.

Brush with barbecue sauce and grill about 10 minutes.

Flip the ribs over, brush with sauce and grill 5 to 7 minutes.

Flip ribs again and brush with sauce and grill about 5 minutes.

Serve immediately.