Make the Chimichurri: COMBINE parsley, cilantro, olive oil, vinegar and garlic in small bowl; set aside.
SEASON mushrooms and bell pepper, if desired, with salt and pepper. Heat large nonstick skillet over medium-high heat and cook mushrooms, peppers and 1/4 cup chimichurri mixture, stirring occasionally, until vegetables soften and brown, about 4 minutes. Remove and set aside.
PREPARE Knorr® Fiesta Sides™ - Mexican Rice in same skillet according to package directions. Stir in pinto beans and mushroom mixture and top with remaining chimichurri.