While the chicken marinates, you should prep all the vegetables. That takes me about 10-20 minutes, depending on how many different vegetables you choose.
Heat a wok or large, high-sided saute pan over high heat. Once hot, add the oil, diced onion, and chopped hard vegetable pieces. Cook, stirring/shaking the pan occasionally, but not so frequently that you inhibit the vegetables from browning on all sides. After about 2-3 minutes, add 2 tablespoons of the marinade to the stir-frying vegetables, then continue cooking another 2 minutes.
Turn the heat down to medium-high, add the soft vegetables to the wok with the hard vegetables, then continue cooking for another 2-3 minutes (still stirring occasionally). Transfer to a plate or bowl, then (carefully because it's hot!) wipe out the wok.
Lift the marinated chicken pieces out of the marinade with a slotted spoon and place in the hot wok (still over medium-high heat). Saute the chicken pieces, stirring occasionally, for 4 minutes or until barely cooked through. Add the remaining marinade to the pan and continue cooking for another 1-2 minutes. The marinade should be bubbling rapidly and the amount of liquid should be reduced by at least half. Add the reserved cooked vegetables and toss everything to combine. After another minute, everything should be heated through.
Serve immediately, on top of brown rice or quinoa and drizzle with your favorite spicy sauce.