I'ved tried this recipes, not bad at all!
1 small onion, chopped
7 cloves garlic
1/2 cup olive oil
1/2 cup vinegar
1/2 cup soy sauce
2 tablespoons chopped fresh rosemary
2 tablespoons Dijon-style prepared mustard
2 teaspoons salt
1 teaspoon black pepper
1 (2 pound) tri-tip steak
Place onion, garlic, olive oil, vinegar, soy sauce, rosemary, mustard, salt, and pepper into the bowl of a food processor. Process until smooth. Place steak in a large resealable plastic bag. Pour marinade over steaks, seal, and refrigerate for about 3 hours.
Preheat the grill for high heat.
Brush grill grate with oil. Discard marinade, and place steak on the prepared grill. Cook for 7 minutes per side, or to desired doneness.