Preheat grill or grill pan to medium-high heat.
Preheat oven to 350°F.
Brush the zucchini and squash with olive oil, season with salt and pepper and place on a hot grill/grill pan.
Grill on each side for 4 to 5 minutes or until slightly softened. Remove from grill and set aside.
Place the tomatillos and garlic in a bowl and toss together with olive oil, salt and pepper.
Pour the mixture onto a baking sheet and roast for 20 minutes or until the tomatillos have softened and slightly caramelized.
Remove from the oven and place tomatillos and garlic into a food processor with the remaining salsa ingredients.
Puree the mixture until smooth, Season with salt and pepper. Set aside.
Melt the butter in a skillet over medium-high heat.
Add the red onion, bell pepper, jalapeno, and garlic and sauté for 3 to 4 minutes.
Add the corn and continue to sauté for 5to 7 minutes. Season with salt and pepper.
Remove from heat and set aside.
Warm the tortillas over a griddle for about 3 minutes on each side.