I remember eating this delicious breakfast while traveling a long time ago and since it was a to go order, I never really remembered the name.  The dish had eggs (scrambled style) mixed with rice. There may have been tortilla chips but I don't remember if they were mixed or on the side.   There may have been other ingredients and I can't remember them but if someone can point them out it may jog my memory. 
Here's some general guidelines I have used in the past:  Small onion = 4 ounces by weight or about ½ cup chopped Medium onion = 8 ounces, or about 1 cup chopped Large onion = 12 ounces, or about 1½ cups chopped Jumbo onion = 16 ounces, or about 2 cups chopped  source The terms are not always completely accurate so use your best judgement. I've often seen large onions that were as big or bigger than "jumbo" according to this data. 