Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper. Heat a grill or grill pan over medium-high heat.
Stir together the flour, oats, pecans, sugar, salt and cinnamon in a medium bowl. Add half the vanilla bean seeds and all the cubed butter. Use your hands, a fork or a pastry cutter to blend the butter into the dry mixture until it is evenly combined in small clumps and crumbles. Spread the mixture on the lined baking sheet and bake until the clumps are golden and crisp, 15 to 20 minutes. Set aside until ready to use, or crumble and store in an airtight container for up to 1 week.
Meanwhile, arrange the peaches cut-side up on a baking sheet or plate. Mix the remaining vanilla bean seeds with the olive oil in a small bowl. Brush the peaches with the mixture.
Add the peaches cut-side down to the grill. Cook, without flipping, until the peaches are charred on the cut side, but not mush, 2 to 3 minutes. Remove the peaches to a serving dish. Top with the crumble. Serve each peach with a scoop of ice cream and some extra crumble.