Combine seasoning ingredients in a large bowl and stir well.
Cut the sirloin into very thin slices, and chop the grains. Add the steaks to the marinade and mix well. Cover and refrigerate for 30 minutes while you prepare the vegetables.
Finely chop the onion into cubes, then rinse and remove the lid from the peas, chop the carrots into matches and chop the pepper.
Heat a heavy-bottomed skillet or a good frying pan over high heat. Once the skillet is hot, add 1 1/2 tablespoons of cooking oil. Immediately add onions (while stirring constantly for 1 minute).
Drain the beef and reserve the marinade. Add the drained beef and stir constantly for 2-3 minutes. (Note: You don't want to scrape the beef all at once or the pan will cool down very quickly; you really want to flip the beef so the juice doesn't come out.) Add the extra sauce to the skillet.
Add the vegetables and continue cooking over high heat for 2-3 minutes, stirring frequently, or the vegetables soften and the sauce begins to thicken. Serve over a bed of hot white rice,