If you put a pan that isn't oven safe in your oven, you may wind up with melted handles, ruined food and toxic fumes. An ovenproof skillet will often have an oven-safe symbol or text on its bottom to let you know that it can tolerate oven temperatures. You can also get to know different materials that are used in pan construction to make your own judgement calls when needed.
Metal and ceramic pans are oven safe. Nonstick coatings on metal or ceramic pans may or may not be oven safe, so you should check the writing on the bottom of these pans or read the manufacturer's guidelines.
Choosing an Ovenproof Pan
Any pan that you typically place directly onto a flame, metal coil burner or induction burner should be able to withstand the heat of an oven. However, the parts of the pan that aren't typically in direct contact with heat may be another matter. Plastic handles and rubber and plastic gaskets and seals are prime candidates for melting and ruining an otherwise perfectly good piece of equipment.
Cast iron pans are oven safe because they are made of nothing but metal. Rather than relying on a material such as plastic for nonstick qualities, they are seasoned with oil or another fat that can stand up to high temperatures. Unless your cast iron pan has handles made of a substance such as plastic that isn't ovenproof, which is extremely rare, the pan will be perfectly suitable for recipes that include oven cooking.
Any dish or pan that is marketed as a baking dish should be safe for oven use. These include casserole pans, baking pans and muffin pans, among others. Many substances used in pan construction such as Teflon and other nonstick coatings are safe up to temperatures of 500 degrees Fahrenheit, which rules them out for use in an ultra-hot oven, such as a wood-fired pizza oven, but makes them safe for typical household oven use.
A Plastic Handle Workaround
If you're using a recipe that requires putting your pan in the oven, but you only have one with plastic handles, you can increase the heat tolerance of your pan by wrapping the handles to limit the heat that will reach them. Aluminum foil will slightly temper the heat that reaches your handles that aren't oven safe but only for very brief cooking periods.
A more effective solution is to wrap the handles of your pan in wet paper towels and then wrap the paper towels with aluminum foil. The paper towels need to be soggy enough that the moisture in them won't evaporate during the time the pan is in the oven. With a setup like this, the handles can never get hotter than boiling water, which is 212 degrees Fahrenheit, a temperature that will still burn your hands if you don't use oven mitts but won't melt the handles of your pot.
Uses for Oven-Safe Pans
Oven-safe pans are ideal for recipes that require long, slow cooking, such as pot roasts and other braised-meat dishes. Rather than placing the pan on the burner and relying mostly on heat forming from a burner underneath the pan, oven cooking surrounds the pan and the ingredients with heat, allowing for even cooking.
Recipes such as frittatas are started on the stove top and finished in the oven. This allows you to finish the recipe by browning rather than just heating from the bottom, as you would if you were cooking exclusively on the stove top. Casseroles are baked for extended periods of time to ensure slow, even cooking and often have a crust with a different texture than the middle. Oven-safe casserole dishes hold heat well and also often make attractive serving dishes.