Place the poha in a colander and rinse it well under running water. Stir the poha gently by using your fingers while rinsing; otherwise it will become mushy at the time of cooking. Once washed, set aside the poha.
Heat oil in a heavy bottomed pan or a wok. Add the mustard seeds, and allow it to crackle.
Add onions and ginger. Sauté over medium heat till light brown in color. Once the onions are tender, add the tomatoes, oats, turmeric powder, steamed vegetables, peanuts, raisins, salt and sugar. Stir to combine and finally add rinsed poha and sprinkle little more water.
Give the poha a gentle stir until all the ingredients come together. Turn the heat to low and cover the pan. Allow the vegetable poha to cook in the steam along with the vegetables. This will take about 3 to 4 minutes.
After 3 to 4 minutes, you will notice the poha has puffed up slightly. At this stage, turn off the heat.
Stir in the juice from one lemon and the coriander leaves. Check the salt and seasonings, and adjust to suit your taste and serve.