Light your grill and set up for direct heat cooking. Using a reliable leave-in thermometer, establish grill temperature at 400° F.
While the grill is preheating, trim ribs by taking off any stray hanging pieces of meat and cleaning up the edges as needed. Remove the membrane on the back of the ribs by grabbing a corner of it with a paper towel for grip and peeling it off.
In a small bowl, whisk together all ingredients for the dry rub. Reserve ¼ cup of the rub and transfer the remaining rub into a shaker bottle.
Season the ribs, starting with the bone side of the ribs first, then flip them over and season the meat side of the ribs. Set the ribs aside while you make the mop sauce.
Bring wet ingredients of the mop sauce to a low boil over medium heat, then whisk in the reserved rub. Reserve one cup of mop sauce and set aside. Keep the remaining mop sauce over very low heat to keep warm while cooking the ribs.
With grill temperature stabilized at 400° F, place ribs over direct heat, bone side down. Close the lid and set a reliable timer for 15 minutes. After 15 minutes, open the lid and mop the ribs with warm mop sauce. Flip ribs, close the lid, and start the timer for another 15 minutes. Repeat this process for 90 minutes.
Remove ribs from the grill and plate them meat side up. Mop the ribs one last time and give them a light sprinkle of rub. Let rest for 5 minutes before slicing and serving with reserved mop sauce.
Notes
There are several ways to cook baby back ribs; the “best” way is totally subjective and completely up to you. Baby back ribs can be smoked low and slow like these smoked spare ribs. They can be baked or broiled if you prefer to cook ribs in the oven. This blog, however, is about grilling baby back ribs, and they’ll be done in 90 minutes.