Yes, you can absolutely use a toaster oven to toast your bagel. In fact, some consider a toaster oven to be even better for toasting bagels as it allows for more control over the toasting process. Simply preheat the toaster oven to your desired temperature, place the sliced bagel on a baking sheet or directly on the rack, and toast for the recommended amount of time, keeping a close eye on it to prevent over-toasting.