Battery Question -- 2xTrojan L16RE, 1500w Inverter?

Most toaster ovens would be just fine with a MSW inverter. Heaters and switches don't care at all about the purity of the AC waveform. Even most with digital controls would probably work fine.

I would note that one pound of propane has as much energy as a few hundred pounds of battery (though, of course, it requires a bit more specialized infrastructure to "recharge" a propane tank). In other words, for dry camping, a gas oven will cook a whole lot more than a toaster oven and a battery bank.