In a large skillet heat oil over medium heat. Add onions.
After onions are translucent, add in ground beef and continue cooking. Add in green bell peppers now if using.
When meat is browned, drain excess grease.
Then add rest of ingredients and mix well. Allow to cook for another 5 minutes.
Serve warm.
Optional: toast gluten free buns in the oven over broil. Simply place buns open face on a baking sheet. Watch carefully so they don't burn. Then rub buns lightly with dairy free butter for restaurant-style buns.
Notes
This homemade sloppy joe mix can easily be made 2-3 days ahead of time and reheated. And can be frozen up to 2 months, thaw and reheat when ready.