Combine Cheddar, cream cheese, scallions, bell pepper, cilantro, jalapenos (if using), orange zest and juice in a medium bowl. Gently stir in crab. Lay tortillas out on a work surface. Spread one-fourth of the filling on half of each tortilla. Fold tortillas in half, pressing gently to flatten.
Heat 1 teaspoon oil in a large nonstick skillet over medium heat. Place 2 quesadillas in the pan and cook, turning once, until golden on both sides, 3 to 4 minutes total. Transfer to a cutting board and tent with foil to keep warm. Repeat with the remaining 1 teaspoon oil and quesadillas. Cut each quesadilla into 4 wedges.