Trim any excess fat or silver skin from the top sirloin roast, leaving a thin fat cap for flavor. Pat the roast thoroughly dry with paper towels — dryness ensures a good sear.

Prepare Garlic Marinade

In a bowl combine the minced garlic (8 cloves), olive oil (4 tbs), kosher salt (3 tbs), freshly ground black pepper (2 tsp), chopped rosemary (1 tbs), thyme (1 tsp) if using, red wine vinegar or lemon juice (1 tbs), and sugar or honey (1 tsp) if desired. Whisk until well combined.

Marinate the Roast

Place the sirloin in a shallow dish or large resealable bag. Rub the garlic marinade all over the surface, pressing it into any scored areas. Cover and refrigerate for at least 2 hours and up to 12 hours. For best flavor, remove from the refrigerator 45–60 minutes before grilling to come up toward room temperature.

Preheat Grill

Set up your grill for two-zone cooking (direct high heat and indirect medium-low). Preheat one side to high (about 450–550°F / 230–290°C) and the other side to medium-low (about 300–350°F / 150–175°C). If using a charcoal grill, bank coals to one side. If using a gas grill, light half the burners.

Sear Over High Heat

Brush the grill grates clean and lightly oil them. Place the sirloin directly over the high-heat zone and sear 2–3 minutes per side, rotating to create a well-browned crust. If the roast is large, sear each long face and ends so the exterior is caramelized.

Finish Over Indirect Heat

After searing, move the roast to the indirect (medium-low) side of the grill. Close the lid and cook until the internal temperature reaches 125°F (52°C) for medium-rare or 135°F (57°C) for medium, about 20–45 minutes depending on roast size. Use a digital instant-read thermometer inserted into the thickest part of the roast to check temperature. Start checking at 15 minutes.

Rest the Roast

Remove the roast from the grill and transfer to a cutting board. Tent loosely with foil and rest for 10–15 minutes. Resting allows juices to redistribute and internal temperature to rise about 5–10°F (3–6°C).

Finishing & Serving

Make Garlic Butter

While the roast rests, combine the softened unsalted butter (2 tbs), minced garlic (2 cloves), and chopped parsley (1 tbs) in a small bowl. Mix until smooth. Taste and add a pinch of coarse sea salt and a grind of black pepper if desired.

Carve Tableside

Using a sharp carving knife, slice the sirloin across the grain into thin, even slices (about 1/8–1/4 inch thick) for tender bite-size pieces. For thicker steak-style slices, cut to desired thickness but still across the grain.

Finish and Serve

Brush or place a small dab of garlic butter onto slices so it melts over the warm meat. Sprinkle a little coarse sea salt and cracked black pepper to taste. Serve immediately, carving tableside if desired, with remaining garlic butter on the side.