It didn't take long for Swindon to take the lead with Peacock opening the scoring for Swindon after only 42 seconds.
On 56 minutes Swindon should have been awarded a penalty for a foul clearly inside the box, but instead a free kick was given on the edge of the area.
Then on 61 minutes Swindon were awarded a penalty for a handball. Jack Smith took the kick and scored to make it 2-0 to Swindon.
On 79 minutes Mkandawire pulled a goal back for Leyton Orient after a goal mouth scamble.
For the final 11 minutes of normal time, and 4 minutes of stoppage time Swindon held on with Leyton Orient having most of the play, and Brezovan being called into action a number of times.
Overall a good win which puts Swindon 3 points above the relegation zone going into Sunday's game at home to Brighton.