Peel and slice the red onion. Slice the mushrooms. Remove the stems and seeds from the peppers, then slice them.
Place your prepped veggies in a large bowl. Drizzle the olive oil over them, then sprinkle in the cumin, coriander, paprika, and salt to your taste. Toss the vegetables until all of them are well coated with oil and spices.
Transfer your veggies to a skillet over medium-high heat. Sauté the vegetables while stirring frequently until they're cooked yet still slightly crunchy, about 8-10 minutes.