An OTG is a combination of an Oven, Toaster, and Grill. An OTG's capacity may go up to 60 litres, whereas a convection microwave's capacity is only up to 32 litres. The comparision between OTG and Microwave Oven OTG is Oven-Toaster- Griller. What is the difference between a Microwave and an OTG? Let's talk about OTG first — 1. OTG (oven, toaster, griller) and microwave ovens have several similar functions. What is an OTG? An Oven, Toaster, Grill (OTG) is a smaller version of a traditional oven.