In a gallon plastic bag, combine half a cup red wine with a fourth of a cup of olive oil, four finely minced garlic cloves, and a teaspoon of kosher salt and freshly ground black pepper.
Shake well to combine, then place your beef tri-tip into the bag with the red wine marinade.
Remove as much air from the bag as possible and seal it shut, working the marinade into the meat.
Let the meat sit in the refrigerator for a minimum of four hours and up to six, turning it over in the bag every half hour or so.
At the end of the marinating process, it's a good time to light the grill.
Fill your grill with charcoal, put down the grate, and light it up. A common mistake people make is lighting the grill just as they're about to put the meat on, when it's a much better idea to allow it to warm up for a short time first.
This lets the meat cook more evenly and quickly and lets you make the most out of your time.
Once the marinade has done its job and the grill is heating up, it's time to get ready to grill.
Take the meat out of the bag and empty the contents into a small saucepan.
Let the meat warm up for at least half an hour before you apply any heat, as this helps to ensure the beef cooks evenly.
This can easily be done at the same time you light the grill, letting both your meat and grill warm up for the same length of time.
Once the beef has gotten closer to room temperature, take it to the grill and place it down onto the hottest part of the grates (near the center).
Cook each side for 10 to 12 minutes each, brushing it down every few minutes with your leftover marinade liquid.
The tri-tip is done when the instant-read thermometer registers an internal temperature temperature of about 130 degrees F at the thickest part.
Once you've taken the meat off the heat, set it on a cutting board and tint it loosely with aluminum foil.
Resting your meat lets it relax and reabsorb its juices, leading to a more tender and flavorful bite.
During the ten minutes or so it takes to rest, the tri-tip will continue cooking for about 5 degrees, reaching 135 degrees Fahrenheit and a perfect medium rare doneness.
As you rest your tri-tip, now is a great time to reduce the leftover marinade into a sauce-like consistency.
Just heat the contents of the sauce pot over medium heat while stirring occasionally.
Add in any juices from the resting meat as you go.
The sauce will need to come to a low boil before it's safe to eat to ensure any bacteria from the raw meat is killed off.
While it isn't meant as a true sauce or gravy, reducing down the leftover marinade can help to intensify the flavors.
Once it's reached a good consistency (not too thick and not too thin), taste and season with more salt and pepper as necessary.
Once your red wine marinated tri-tip has rested and your sauce has reduced, it's time to eat.