Preheat your oven to 425°F (220°C).

In a small bowl, mix together the olive oil, minced garlic, chopped rosemary, salt, and black pepper.

Rub the marinade all over the tri tip, ensuring it’s well coated.

Transfer the seasoned tri tip to a roasting pan, fat side up.

Put the roasting pan in the preheated oven and roast for about 1 hour, or until a meat thermometer reads 135°F (57°C) for medium-rare.

Once cooked, remove the tri tip from the oven and cover it loosely with aluminum foil.

Rest the meat for at least 15 minutes before slicing.

Using a sharp knife, slice against the grain to ensure maximum tenderness.

Plate the slices and serve with your favorite sides.