Take 1 cup of oats and grind them into a fine powder using a mixer grinder.
In a mixing bowl, add the ground oats, 1/2 cup gram flour (besan), 1/4 cup finely chopped onions, 1/4 cup grated carrots, 1/4 cup chopped capsicum, 1/4 cup chopped tomatoes, 1/4 cup chopped coriander leaves, 1/2 teaspoon grated ginger, 1 chopped green chili, 1/2 teaspoon cumin seeds, 1/2 teaspoon red chili powder, 1/4 teaspoon turmeric powder, and salt to taste.
Gradually add water to the mixture and whisk well to form a smooth batter of pouring consistency. Let the batter rest for 10-15 minutes.
Heat a non-stick tawa or griddle over medium flame. Grease it lightly with oil.
Pour a ladleful of batter onto the tawa and spread it evenly in a circular motion to form a thin chilla.
Drizzle a few drops of oil around the edges of the chilla and cook for 2-3 minutes until the bottom turns golden brown.
Flip the chilla and cook the other side for another 2-3 minutes until golden brown.
Transfer the cooked oats chilla to a serving plate and repeat the process with the remaining batter.