Heat the avocado oil in a large thick-bottomed pot (I use my Dutch oven) and add the chopped onion. Sauté, stirring occasionally, until the onion has softened, about 5 to 8 minutes.
Scoot the onions off to the side and place the ground beef in the center of the pot. Allow it to brown for 3 to 4 minutes before using a spatula to break it into small pieces.
Stir in the garlic, dried oregano, mushrooms, red bell pepper, sea salt and liquid aminos (or soy sauce) until well-combined.
Add the chopped cabbage to the pot, then cover it with a lid and cook for 5 to 10 minutes, or until the cabbage has softened, stirring every few minutes.
Remove the lid and continue cooking until much of the liquid has evaporated off and the cabbage reaches your desired level of doneness, about 8 to 10 minutes.
Serve in bowls and enjoy!