Cook butter beans according to package directions and drain and cool completely. This will take about 20 minutes.
While beans are cooking, heat grill to medium-high. Brush corn, red pepper, and onions with olive oil. Place on grill and close lid.
Turn corn every 4 to 5 minutes until all sides are charred. Flip red peppers and onion after 5 minutes and remove from grill once second side has grilled for 4 to 5 minutes. Let cool and then cut corn from cobs and chop pepper and onion into ½-inch pieces.
In a large bowl, combine mayonnaise, garlic, salt, and pepper. Stir to mix and add butter beans, corn, red pepper, onion, tomatoes, and jalapeno. Toss to combine. Sprinkle cilantro on top and refrigerate for at least 2 hours. Serve chilled.