Preheat the oven to 375. Spray a 13 x 9 baking dish with nonstick spray.
In a large bowl, whisk together the eggs, milk, cream, sugar, orange zest and 1/2 the orange juice.
Add the croissant pieces and the berries to the bowl with the custard and stir to coat evenly (I found my hands worked best!). Pour into the prepared baking dish and cover with foil.
Bake for 40 minutes in the preheated oven. Uncover and bake for an additional 30 minutes.
Combine the strawberries, sugar, cornstarch, remaining orange juice and Grand Marnier in a small saucepan. Bring to a simmer, stirring frequently, for 10-15 minutes, until the mixture has a thick syrupy consistency. Set aside and cool to warm.
Spoon the bread pudding on a plate, spoon the sauce over, and serve.