The perfect frittata will have golden edges, and a center that is set, but not overcooked. The secret to knowing when the frittata is done is with “the jiggle” test. If you shake the pan and the frittata has a little jiggle to it, then the frittata is done. Depending on how powerful your oven is, you may want to start checking the frittata at the lower end of the bake time.