Prep Your Ingredients. Preheat your oven to 425°F. Slice the bell peppers and onion into thin strips. Pat the shrimp dry with paper towels to ensure they roast rather than steam.
Season Everything. In a large mixing bowl, combine the shrimp, peppers, and onion. Drizzle with olive oil and sprinkle the fajita seasoning, salt, and pepper. Toss until everything is evenly coated.
Arrange on the Sheet Pan. Spread the shrimp and veggies in a single layer on a large sheet pan. This ensures even cooking and prevents overcrowding.
Roast. Bake in the preheated oven for 10-12 minutes, flipping the shrimp and veggies halfway through. The shrimp should be pink and opaque, and the veggies tender with slightly charred edges.
Add the Finishing Touch. Remove the pan from the oven and immediately drizzle lime juice over the shrimp and veggies. Toss gently to coat.
Serve and Enjoy. Serve warm with tortillas and your favorite toppings. Garnish with fresh cilantro for a burst of flavor.