Og Melech haBashan is certainly one of the most colourful Midrashic figures. According to the Midrash, he survived the flood, lived hundreds of years, stood many hundreds of feet tall, and could lift mountains.
But in the peshat, we have less information. The only information that might indicate Og's exceptional size is derived from the proportions of his bed! It is described in Devarim 3:11. There we are told about an iron bed-frame 9 cubits (amot) by 4 cubits i.e. 2 metres by 4.5 metres. Not small! In fact, a very large (9-10 ft.?) man, but not a giant of the proportions ascribed by the Midrash! (Part of the midrash could be from the fact the the bed is called an "eress" sometimes indicating a baby's cradle. Of course if this was Og's bed as a baby, we would be able to extrapolate a far larger adult size. However, eress can simply mean bed. See , fro example, Tehillim ch.6 - Tachanun.)
In my daughter's school (Orot Etzion) they did a lovely activity to illustrate Og's large size according to Peshat. They went to the playground. They drew a rectangle shape 2x4.5 on the floor. Then the teacher asked the class to lie down in "Og's bed". The entire class fit in the rectangle ... with room to spare! This gave them a great peshat understanding of the large physical dimensions of the mythical figure. A wonderful, simple pedagogic tool. And lots of fun too!