In a bowl combine the granulated garlic, chopped rosemary, black pepper and salt. Brush the Tri-Tip with 2 tablespoons of olive oil and rub the seasoning mix over the meat. Cover in plastic wrap and marinate in the refrigerator for an hour or overnight. Remove the meat from the refrigerator 30 minutes prior to cooking.
In a bowl combine all chimichurri ingredients (bell pepper, parsley, remaining olive oil, lemon juice & zest, red pepper flakes and pinch of salt). Cover and refrigerate for an hour. Return to room temperature before serving.
Preheat an outdoor grill to medium-high heat.
Set the Tri-Tip on the grill grates and close the lid cooking for 15 minutes. Turn the meat and continue to grill for an additional 15 minutes. 5. Remove the Tri-Tip and set on a cutting board covering partially with foil. Let rest for 10 minutes to let the juices settle.
Thinly slice the Tri-Tip and serve the bell pepper chimichurri over the meat.