Trim fat layer from tri-tip. Mix marinade ingredients, combine with tri-tip and refrigerate for 1 hour.
Heat Big Green Egg to 250 degrees with convEGGtor installed for indirect cooking. Cook tri-tip on grillto 120 degrees and remove (can take anywhere from 20 minutes to 1 hour).
Remove convEGGtor and heat Big Green Egg to 500 degrees. Sear tri-tip on grill for 2-3 minutes per side. Slice against the grain and serve.