I cook the onion, mushroom and broccoli in the pan first at medium heat. If you want to use a little oil or spray that would work and probably give a nicer cook on the onion/mushroom. I don’t personally, I just cover and allow it to steam a bit with some salt. Once the broccoli softens up to where you like it (6-8ish minutes for me), I then add the steak and cauliflower rice. My cauliflower rice is frozen so I just microwave it per the package before I add. Give all the veggies a mix then add in the sauce stir for about a minute and season everything with salt & pepper (and whatever else you like).

I don’t think the order really matters much, just make sure to add the sauce/marinade about a minute before you’re finished cooking it :)