Prepare outdoor grill for direct grilling over medium-high heat. Slice ½-inch from the top of bell peppers; remove seeds and inner membranes.
Prepare quinoa as label directs; stir in seasoning.
In large skillet, heat tomatoes and chilies with their juice, beans and corn to a simmer over medium-high heat, stirring occasionally. Stir in spinach; cook 3 minutes or until spinach is wilted, stirring occasionally. Remove from heat; stir in salt and quinoa mixture.
Fill peppers with quinoa mixture; sprinkle with cheese. Place peppers, cheese side up, on hot grill rack; cover and cook 5 minutes or until grill marks appear. Turn off 1 side of grill; place peppers over unlit side of grill, cover and cook 15 minutes or until heated through and cheese melts.