Grill brats over medium heat, turning frequently, till browned.
Meanwhile, heat oil in skillet. Add onion & green peppers. Saute till onions & peppers are tender. Add tomato and mushrooms; toss in Mrs. Dash seasoning & basil. Continue cooking, stirring frequently until the tomatoes and mushrooms are hot through.
Place a brat one each bun and top with vegetable mixture.
(If you don't have some way to grill the brats, you can make this ahead and heat up in microwave when ready to serve).