In a large bowl, toss bell pepper, broccolini, and onion in 1 tablespoon of olive oil until thoroughly coated. Season with salt and grill in the panini press in a single layer until the vegetables begin to soften, about 5-7 minutes.
Remove the vegetables from the panini press and set aside. Lightly brush both sides of the polenta with olive oil, then grill, flipping once, until crisp and beginning to brown, about 15 minutes.
To serve, place a spoonful of vegetables on a plate, top with a few slices of polenta, and top with oven roasted corn and black bean pico de gallo and avocado.