Can you put corningware bowl in oven just on metal rack?

Yes, but the oven should be preheated if the bowl is made of pyrex or similar glass. Ceramic Corningware is more durable. The lids of Corningware are usually made of pyrex and need special handling, when removed from the oven/stovetop they should not be placed on a cold surface such as the metal drainage board of a kitchen sink. Place them on a thick tea towel, wooden board, etc, to prevent sudden temperature change which can result in the glass shattering. Similarly, the lids should be clear of food cooking within the dish, for example if roasting meat in a lidded casserole in the oven, the lid can crack or shatter if it is touching the roast, there should always be clearance between the top of the food and the lid.