To prepare tri-tip: Season tri-tip generously with salt and pepper, to taste, on all sides. Rest at room temperature about 30 minutes.
To prepare chimichurri beet sauce: In food processor, combine pickled beets, parsley, cilantro, minced garlic, red wine vinegar, olive oil, fresh oregano, red pepper flakes, salt and pepper. Pulse until mixture is well combined and forms chunky sauce. Adjust seasoning, to taste.
Heat grill to 350 F and prepare for two-zone grilling.
Place tri-tip over indirect heat. Close lid and grill 30-40 minutes, flipping every 5-7 minutes, until internal temperature reaches 125 F for medium-rare.
Move tri-tip to direct heat and grill 2-3 minutes per side, or until internal temperature reaches desired doneness (135 F for medium-rare).
Transfer tri-tip to cutting board and rest 10-15 minutes.
Slice tri-tip against grain into thin slices. Arrange slices on serving platter and drizzle with chimichurri beet sauce. Serve extra sauce on side for dipping.