If using wooden skewers, soak them for 30 minutes to prevent them from burning during grilling. Fill a sheet pan with water, spread the skewers inside, and let them soak.
Remove the marinated pork loin from the bag and place it on a plastic cutting board. Discard the packaging and juices (marinade). Cut the pork loin into even-sized 1-inch cubes.
Chop any veggies (bell pepper, onions, or both) into 1-inch-square pieces.
Assemble:
Thread the pork and veggies through the skewer, always poking through the middle of each ingredient to prevent it from sliding or falling off. With onions, I usually grab a couple of layers at a time. Place the assembled kabobs on a baking sheet for easy transfer to the grill. Depending on the size of your skewer, this recipe makes 6 to 8 kabobs.
Grill:
Preheat the grill with the lid closed to medium-high heat. If your grill has a temperature gauge, it should read between 375F and 400F; otherwise, preheat for 10 to 15 minutes. Use grilling tongs to grease the grates by wiping a paper towel soaked in oil over the grates. This step is especially important to prevent the skewers from sticking.
Place the kabobs on the grill across the grates (not parallel). Sear the first side with the lid open for a few minutes, then close the lid and cook for about 5 minutes. Open the grill, flip the kabobs over by picking them up from the middle using grilling tongs. Then, close the lid and cook the second side for about 5 more minutes. Total cooking time will vary depending on the thickness of the pork pieces and your grill. Pork will need to be cooked to 145F.
Remove the kabobs from the grill to a tray, then cover them with foil to keep warm while you finish grilling or let them rest for 5 minutes before serving.
Leftover Storage:
Remove the grilled meat from the skewers and store it in an airtight container. They'll keep in the fridge for up to 4 days. To reheat, you can microwave them for about 45 seconds to 1 minute, depending on how much you're heating up. To warm them up in a pan, take them out of the fridge for 10 minutes first (so they're not cold), drizzle a little olive oil on a non-stick pan, then heat them up over medium heat until warmed through.
Notes
Using a plain pork loin? No problem. Mix 2 tablespoons of olive oil with 1 teaspoon of salt, 1 teaspoon of garlic powder, and ½ teaspoon of ground pepper in a large bowl. Add the cubed pork loin to the bowl, and toss to coat it with the seasoning. Then, thread it through the skewers and grill.