Start by pre-heating your oven to 400 degrees F. Poke fork holes all over the sweet potato (you don't have to go crazy, try 4 per side). Place the sweet potatoes on a baking sheet and drizzle with olive oil. Bake until fork tender, about 1 hour.
While the sweet potatoes are cooking, chop up the corned beef and Swiss cheese into little squares and toss it in a bowl with the chopped red onion and green onion. Set aside.
When the sweet potatoes are done, allow them to rest until cool enough to handle. Make a slit along the length of the top of the sweet potato to open it up, and scoop the insides out into the bowl with the corned beef. Be careful not to poke through the skin of the potato! I usually leave about 1/4 of an inch of insides.
Mix the sweet potato and corned beef mixture with the thousand island dressing until everything is well combined. At this point you can add a pinch of salt and pepper if you like (I didn't add any, but that's my preference).
Scoop the mixture back into the sweet potato shells. You have the option to top them with more sliced Swiss cheese if you like! Place the baking sheet back in the oven and bake for another 8 minutes.
Remove the baking sheet from the oven and transfer the sweet potatoes to a plate. Sprinkle with more chopped red onion and green onion, a drizzle of thousand island dressing and some sauerkraut! Enjoy!