sure, IF your convection oven/microwave needs less than that to operate, and IF you are also not using other 120v items at the same time, and IF you don't operate it too long.
Any appliance or device which demands a lot of amps, like the oven, microwave, or electric heater, can quickly deplete the batteries.
what is 'too long'? the Battery levels will determine how long you can successfully run anything off of the Inverter - if the levels are at full charge, then you can certainly run it much longer than if your batteries are already depleted - most any Inverter has a built-in LBCO(low battery cut off), which automatically cuts off the Inverter should the battery level readings fall below a set number, such as 10.0, to save the batteries from further depletion.
If you have some solar and want to use it during good sun hours, then the incoming solar power will help offset the convection oven during it's run...
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