Preheat grill to 350-400°F and place cast iron pan on grill.
Slice onions and peppers into long strips. Do not chop.
Place sausages on preheated grill and poke 4 holes in each sausage with a toothpick or knife to prevent splitting and bursting while cooking.
Warm oil in pan and add onions and peppers. Season with SPG to your liking. Cook until softened, about 10 minutes.
Cook sausages to an internal temperature of 160°F turning several times while cooking. About 10-15 minutes.
Grill buns for 30 seconds if desired and remove to a serving platter.
Remove sausages when finished and place onto buns. Top with grilled onions and peppers. Serve with condiments of your choice. (Mustard, ketchup, relish...)
Video
Notes
Use a meat thermometer to determine when the sausages are finished cooking. This prevents under or over cooking.
Turn down the temperature or move sausages away from direct heat if they are flaring up from the fat falling onto the flames. Sausages are fatty and flare ups are common.
Clean grill with a grill brush after preheating to remove any leftover food from previous cooks. Rubbing an onion cut in half on the grates will help disinfect the grill and help remove old food.