Scrub and pat potatoes dry. Pierce potatoes all over with a fork and bake in the oven, directly on rack, until soft (about 40 to 45 min. depending on the size of your potatoes).
In a bowl, combine all the ingredients for the taco seasoning.
Melt some cooking fat in a skillet over medium-high heat.
Add the onions and cook until soft and fragrant, about 3 to 4 minutes.
Add the ground beef to the skillet and cook until browned.
Sprinkle the taco seasoning onto the beef, and stir to combine. You may want to add 1 or 2 tbsp. of water if the meat is too dry or the seasoning is not mixing well.
Cook the ground beef another minute or two and set aside.
Using a sharp knife, make a lengthwise slit in each potato and push ends of each potato toward each other to open.
Fill the potatoes with the ground beef and top with all the remaining vegetables.