Ok, so I have to confess that I often have a problem with over cooking tri tip. It's a really lean cut so it needs to be cooked at high heat for a short time. It can't really be slow cooked, unless you're interested in a rock. And it tends to look a bit more pink than a lot of meats...and I'm not a bloody rare meat eater so I tend to over do it. I found great cooking tips here.
I always have to change things up a bit so I did a wet marinade for 90 minutes, then dried the meat and did a peppery dry rub for 30 minutes. The meat was at room temperature for 2 hours total.
My marinade consisted of everything I had in the fridge, sounds gross but it worked.
2 1/4lb tri tip roast
1/2 c diet cola
1/2 c beer (I used IPA, but that's just what we had)
2T olive oil
2T worchestershire sauce
2T barbecue sauce
1t garlic powder
1t onion powder
a bit of HP Sauce
a bit of horseradish
Toss in a zipper bag and let it sit at room temp 90 minutes
Drain marinade and thoroughly dry meat with paper towels
Rub meat with dry rub and let sit for 30 minutes
4 garlic cloves, chopped fine
1/2t chili powder
Preheat oven to 550 for 5 minutes
Cook at 550 for 5 minutes and reduce heat to 450 (the high heat seals in the juices)
Cook at 450 for 15 minutes and start checking temperature.
Make sure the internal temperature is between 115 and 130 (I wouldn't go beyond 130 because overcooking kills the meat, I know, I've done it enough)
Don't cut into the meat, it will look pinker than you want and you'll lose the moisture
Let the roast sit for at least 10 minutes to help complete the cooking without losing the juices
Cut in thin strips along the grain to serve.
I pretty much followed the directions on the site I listed, except for the high heat at the beginning which really get's a nice glaze on the meat. Holy cow, so good. My husband was seriously stoked on the tri tip. And we had plenty leftover for sandwiches! Enjoy!