Heat the olive oil in a large saucepan over medium-high heat. Add the bison and 1/2 teaspoon of salt, and cook 3 minutes until lightly browned, stirring to break up the meat.
Add the green onion, oregano, and red pepper flakes, and saute for 1 minute.
Add the bell peppers and remaining salt. Cook about 5 minutes, stirring occasionally.
Add the tomatoes and bring the mixture to a boil. Reduce heat to a simmer and cook the sauce uncovered for about 25 minutes, until it thickens. Stir in the spinach.
Add more salt and black pepper, to taste.
Serve over pasta, zucchini noodles, or spaghetti squash. Enjoy!