In a mixing bowl, whisk together soy sauce, olive oil, red wine vinegar, brown sugar, minced garlic, black pepper, onion powder, and dried rosemary.

Trim any excess fat from the tri tip.

Place the tri tip in a resealable plastic bag or shallow dish, and pour the marinade over it.

Seal the bag or cover the dish, and refrigerate for at least 2 hours, or up to overnight.

Preheat your grill to medium-high heat or your oven to 400°F.

Take the tri tip out of the marinade and pat it dry with paper towels.

Grill the tri tip for about 20-25 minutes per side, or roast it until it reaches your desired doneness.

Let the tri tip rest for about 10 minutes before slicing.