Melt the butter in a 12-inch nonstick skillet over medium heat. Add the onion and ¾ teaspoon salt and cook, stirring often, until softened, 5 to 7 minutes. Stir in the garlic and cook until fragrant, about 30 seconds. Stir in the orzo and cook, stirring often, until most of the grains are golden, about 5 minutes.
Carefully stir in the broth and bring to a boil, then reduce the heat to medium-low and simmer, stirring occasionally until all of the liquid has been absorbed and the orzo is tender, 10 to 12 minutes. (Be careful not to cook at too high of heat at this point because the liquid will evaporate instead of cook the orzo and you’ll be left with undercooked pasta.)
Off the heat, stir in the peas, Parmesan, and parsley and let sit until the peas are warmed through, about 2 minutes. Season with salt and pepper to taste and serve with the lemon wedges.
Notes
Vegetables: I often substitute other veggies for the peas, like shredded zucchini, so use your imagination and choose veggies you love (or leave them out)!