No one wants chewy tri tip, so don’t let it happen to you!  The biggest keys to tender tri tip are to: 1. Massage the oil into the meat. Don’t skip this part! You can tenderize your roast now with oil and a free massage, or tenderize it later via chewing.  2. Marinate. 8 hours is ideal. 3 days is great too (but not longer!) If you only have an hour or even 15 minutes, guess what, you're still going to get a great roast--as long as you massage the oil into the meat! However, the longer you marinate, the more flavor and tenderness there will be. 3. Remove meat from the refrigerator 30-40 minutes before cooking, so that it starts cooking at room temperature. 4. Use a meat thermometer! Don’t overcook! Remember, the temperature climbs for about 5 minutes after the meat is off the grill. Take the tri tip off the heat once it reaches 135 degrees for a medium rare tri tip, or 5 degrees below your preferred doneness. Follow the slicing instructions! Much of the toughness of a slice of meat comes from cutting it incorrectly. Follow the slicing instructions above.