Comparision of donation power There is an R an organic group connected to either Oxygen or Nitrogen. R is such a group which has almost zero electronic effects (Resonance effect and inductive effect). I want to ask if N or O are to donate a lone pair then which one will have higher donating capacity?

According to my opinion  it should be Oxygen as it is more electronegative than Nitrogen but I'm still not confident and want some proof considering other factors also and neither do I have an answer.
...According to my opinion it should be Oxygen as it is more electronegative than Nitrogen...


It's correct that oxygen is more electronegative than nitrogen. However, this makes an oxygen group a poorer electron donating group than the corresponding nitrogen group. Electronegativity means that the atom is less willing to give up the electrons. Nitrogen is more willing to give up (donate) its electrons because it is less electronegative.