In 13x9-inch baking dish, combine half & half, eggs, sugar and cinnamon; salt to taste. In a medium bowl, combine 2 cups blueberries, orange juice and zest.
Cut a slit in the back of each croissant creating a pocket; fill with ½ cup blueberry mixture. Place in egg mixture, coating both sides. Let stand 2 minutes; turning often.
In large skillet, over medium heat, melt enough butter to coat skillet. Place croissants in skillet; cook until golden on both sides (about 4 minutes). Repeat as needed with remaining croissants.
Add remaining blueberries to same skillet and sauté until heated through. Spoon berries over croissants.