How do I bake chicken that's already marinated?

Stand on one foot and bark. Then put them in the oven an bake as usual. I guarantee they will turn out fine.

Not sure what the real question is here...marinated baked chicken is cooked the same way non marinated chicken would be.

Put them in the oven and bake.

If you want to go a bit better. A paper bag, some panko bread crumb--or crushed corn flakes a 1/2 cup of flour, a tsp of cornstarch. Paprika, salt, and pepper. And 'shake and bake'. Make sure the chicken is moist, a bit of water will help or the marinade, so the mixture will stick.