Brush pears and onions with olive oil. Place on grill and close lid. Grill turning once, until grill marked and softened, about 3 minutes. Remove from grill and set aside.
Meanwhile, on lightly floured surface, roll out dough to 16 x 12-inch (40 x 30 cm) rectangle; transfer to a baking sheet. Brush dough with remaining oil and place oil side down, directly on grill. Grill uncovered until bubbles form on top and grill marks form on bottom, about 3 minutes (do not worry if dough sags a bit when first placed on grill - as long as it has been preheated the dough will quickly stiffen up). Use tongs to flip pizza; close lid and grill until bubbly and underside is browned, 3 minutes. Transfer back to baking sheet.
Spread pesto lightly over top of pizza. Top with pear slices, onion rings, prosciutto and crumbled cheese. Return pizza on the baking sheet back to grill, cover and grill just until cheese softens, about 2 to 4 minutes.
Remove from grill and transfer to cutting board. Sprinkle with arugula, slice and serve.
Tip: If you want to make this recipe indoors, follow the instructions for the pears and onions using a grill pan over medium high heat and bake the prepared pizza on a parchment-lined rimmed baking sheet in the bottom third of a 450F (230C) oven until crust is cooked underneath and the cheese is melted and bubbling, about 15 to 20 minutes.
Per serving: about 240 calories, 9g protein, 11g total fat (3g saturated fat), 29g carbohydrates, 2g fibre, 15mg cholesterol, 370mg sodium. %RDI: iron 10%, calcium 10%, vitamin A 8%, vitamin C 4%