Heat a grill pan over medium heat (or preheat an outdoor grill). Brush the corn with vegetable oil, sprinkle with a little salt and grill, turning, until slightly charred, about 10 minutes. Set aside to cool.
In a large skillet, melt the butter over medium heat. Add the red onion, garlic, bell peppers and jalapeño. Stir and cook the veggies until they?re soft and golden, about 5 minutes. Set aside to cool slightly.
Cut the corn kernels off the cobs. (You can stand the cob in the center of a Bundt pan to keep the kernels from winding up all over the universe!)
In the bowl of a mixer fitted with a paddle attachment, combine the cream cheese, mayonnaise, sour cream and two-thirds of the monterey jack. Mix on low speed until combined. Add the scallions, veggie mixture, corn and canned chiles in their liquid. Mix until just combined.
Spread the mixture in a 3-quart baking dish and sprinkle with the rest of the monterey jack and a little chili powder. (At this point, you can cover the pan with foil and keep it in the fridge for up to 2 days. Just let it sit at room temperature for 30 minutes before baking.)
Preheat the oven to 350 degrees F. Bake the dip until bubbling and golden, 20 to 22 minutes. Remove from the oven and serve warm with tortilla chips.