Milligan dominated the race from the start and was able to dictate pace over the distance to the chequered flag, though behind him Michael Scott had forced his way through the field to a podium and International Motorsport's Connor Adam hung on to maintain his title hopes.
On his charge through the field, Scott tangled with Tom Alexander mid-corner, the latter spinning off into the infield before regaining the track. Scott also set fastest lap of the race, a 1:37.949 on lap 3.
Another local, Jaden Ransley, was quick in the opening laps and showed true racecraft to hang on as the podium battle swept over him. He finished fourth, two second clear of leading rookie Jordan Baldwin.
Tom Alexander dropped tothe rear of the field while rejoining the race and finished eighth. The former Cantabrian has been battling illness and had missed free practice during the week.
New inductee Sam Wallace made a clean start to the championship, finishing behind Alexander and ahead of Sam Wright, the Championship's youngest competitor, in the Tony Richards Toyota car.
Toyota 86 Championship round four, race one
1 Jack Milligan
2 Michael Scott
3 Connor Adam
4 Jaden Ransley
5 Jordan Baldwin
6 Bramwell King
7 Peter Vodanovich
8 Tom Alexander
9 Sam Wallace
10 Sam Wright