Finely dice the yellow onion into 1/2-inch pieces and mince the garlic head (about 2 tablespoons). Cook the diced onion in a skillet over medium heat with a bit of oil until completely softened and translucent, about 5-7 minutes, then set aside to cool. While the onion cooks, finely chop the fresh parsley and have all your seasonings and other ingredients measured and ready. I find prepping everything before mixing ensures the meatloaf comes together quickly and evenly.

In a small cup or bowl, combine the breadcrumbs and milk, stirring to form a paste, then let it sit for 5 minutes to fully absorb the liquid. In a large mixing bowl, add the ground beef, cooled onion, minced garlic, eggs, and breadcrumb paste from above. Pour in the Worcestershire sauce, horseradish mustard, yellow mustard, parsley, and all-purpose seasoning. Using your hands (I find this gives the most even distribution), gently mix everything together until just combined—avoid overmixing as this can make the meatloaf dense and tough. Stop mixing once everything is evenly incorporated but still slightly loose.

Line a large baking sheet or smoking tray with parchment paper for easy cleanup. Transfer the meatloaf mixture onto the prepared surface and shape it into a loaf approximately 9 inches long and 5 inches wide, leaving some space around it for smoke to circulate. Sprinkle the outside of the shaped meatloaf with the remaining 1 tbsp of all-purpose seasoning, using your hands to gently press it into the surface for better adhesion and flavor development.

In a saucepan, combine the ketchup, molasses, honey, brown sugar, apple cider vinegar, Worcestershire sauce, and hot sauce. Stir well to combine all ingredients smoothly, then place over medium heat and bring to a gentle simmer. Let the glaze simmer for 5 minutes, stirring occasionally, so the flavors meld together and the sugar dissolves completely. Remove from heat and set aside—the glaze should have a rich, glossy consistency that will coat the meatloaf beautifully.

Preheat your smoker or grill to 250°F with smoke running if available. Place the shaped meatloaf directly on the grate (or keep it on the parchment if needed for your setup) and smoke for 1 hour without any glaze. After the first hour, brush a generous coat of the prepared glaze from Step 4 over the top and sides of the meatloaf. Continue to smoke for another 1.5 to 2 hours, basting the meatloaf with additional glaze every 30 minutes—this builds layers of flavor and creates a beautiful caramelized exterior. I like to save some glaze to serve on the side rather than using it all for basting, giving diners the option to add more.

Using an instant-read thermometer inserted into the thickest part of the meatloaf (avoid touching the pan), check that it has reached 160°F internal temperature—this is the safe minimum temperature for ground beef. Once it reaches temperature, remove the meatloaf from the smoker and let it rest on the pan for 5-10 minutes without cutting into it; this allows the juices to redistribute and keep the meatloaf moist when sliced. Transfer to a serving platter, slice, and serve with extra glaze on the side if desired.