Fill large saucepan approximately 3/4 full of water. Bring to a boil over high heat and add Brussels sprouts. If sprouts are extra large, cut in half lengthwise. Cook uncovered until crisp tender, about 2 to 3 minutes; drain.
Mix the lemon pepper seasoning and mustard in a small bowl and set aside
Heat the olive oil in a large skillet or wok over high heat. Add the Brussels sprouts and stir fry until their edges just begin to turn golden, about 1 to 2 minutes
Sprinkle the lemon pepper mustard mixture over the sprouts to taste. Serve immediately.