Balsamic Portobello Burgers with Bell Pepper and Goat Cheese

Name: Balsamic Portobello Burgers with Bell Pepper and Goat Cheese
Ingredients: 1/4 cup olive oil, plus more for grates; 1/4 cup balsamic vinegar; 3 garlic cloves, minced; Coarse salt and ground pepper; 1 red bell pepper (ribs and seeds removed), cut into 4 equal pieces; 8 portobello mushrooms (about 1 pound total), stems removed; 4 hamburger buns; 5 ounces fresh goat cheese, cut into 4 equal slices; 4 lettuce leaves