Fresh ground chorizo

This is determined by the outcome you desire. You can certainly safely cook fresh chorizo in the oven. You just need to be sure it reaches at least 150 F (65.5C). Browning it on the stove first will at least partially cook it (if not fully cook it), but it could also add caramelized notes and texture that is desirable in your final product. So, it really depends on your recipe.