In a large bowl, combine the coleslaw mix, diced green pepper, and sliced onion.
In a saucepan, whisk together the oil, vinegar, sugar, salt, and pepper. You can experiment with different vinegars here. Try a sweeter option like apple cider vinegar, or a more robust flavour with red wine vinegar.
Bring the dressing mixture to a low simmer on the stovetop. Heat until the sugar dissolves, then slowly whisk in the olive oil. Bring to a boil and cook for one minute.
Let the dressing cool slightly, then pour it over the coleslaw mixture in the bowl. Toss well to coat everything evenly.
Cover the bowl and refrigerate for at least 24 hours before serving. This allows the flavours to meld and the cabbage to soften slightly. The coleslaw can be stored in the fridge for up to 5 days.
